Semiconductor thin film forming system

ABSTRACT

In a semiconductor thin film forming system for modifying a predetermined region of a semiconductor thin film by exposing the semiconductor thin film to a projected light patterned through a pattern formed on a photo mask, the system includes a mechanism (opt 20 ′) for uniformizing the light for exposure in a predetermined area on the photo mask. This system can provide a crystallized silicon film having a trap state density less than 1012 cm −2  and can provide a silicon-insulating film interface exhibiting a low interface state density.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/612,551, Filed Jul. 7, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system for the formation of a silicon thinfilm and a good-quality semiconductor-insulating film interface. Suchsilicon thin films are used for crystalline silicon thin filmtransistors, and such semiconductor-insulating film interfaces areemployed for field effect transistors. The invention also relates to asemiconductor thin film forming system by the pulsed laser exposuremethod. Such semiconductors include, for example, silicon germanium(SiGe), silicon carbide (SiC), and other silicon compounds, and GaAs,GaN, CuInSe₂, ZeSe, and other compound semiconductors. In addition, theinvention relates to a system for the manufacture of driving elements ordriving circuits composed of the semiconductor thin films or fieldeffect thin film transistors for displays and sensors, for example.

2. Description of the Related Art

Typical processes for the formation of a thin film transistor (TFT) on aglass substrate are a hydrogenated amorphous silicon TFT process and apolycrystalline silicon TFT process. In the former process, the maximumtemperature in a manufacture process is about 300° C., and the carriermobility is about 1 cm²/Vsec. Such a hydrogenated amorphous silicon TFTformed by the former process is used as a switching transistor of eachpixel in an active matrix (AM) liquid crystal display (LCD) and isdriven by a driver integrated circuit (IC, an LSI formed on a singlecrystal silicon substrate) arranged on the periphery of a screen. Eachof the pixels of this system includes an individual switching elementTFT, and this system can yield a better image quality with lesscrosstalk than a passive matrix LCD. In such a passive matrix LCD, anelectric signal for driving the liquid crystal is supplied from aperipheral driver circuit. In contrast, the latter polycrystallinesilicon TFT process can yield a carrier mobility of 30 to 100 cm²/Vsecby, for example, employing a quartz substrate and performing a processat high temperatures of about 1000° C. as in the manufacture of LSIs.For example, when this process is applied to a liquid crystal displaymanufacture, such a high carrier mobility can yield a peripheral drivercircuit on the same glass substrate concurrently with the formation ofpixel TFTs for driving individual pixels. This process is thereforeadvantageous to minimize manufacture process costs and to downsize theresulting products. If the product should be miniaturized and shouldhave a higher definition, a connection pitch between an AM-LCD substrateand a peripheral driver integrated circuit must be decreased. Aconventional tab connection method or wire bonding method cannotsignificantly provide such a decreased connection pitch. However, if aprocess at high temperatures as in the above case is employed in thepolycrystalline silicon TFT process, low softening point glasses cannotbe employed. Such low softening point glasses can be employed in thehydrogenated amorphous silicon TFT process and are available at lowcosts. The process temperature in the polycrystalline silicon TFTprocess should be therefore decreased, and techniques for the formationof polycrystalline silicon films at low temperatures have been developedby utilizing a laser-induced crystallization technique.

Such a laser-induced crystallization is generally performed by a pulselaser irradiator having a configuration shown in FIG. 1. A laser lightsupplied from a pulse laser source 1101 reaches a silicon thin film1107, a work, on a glass substrate 1108 via an optical path 1106. Theoptical path 1106 is specified by a group of optic devices includingmirrors 1102, 1103, and 1105, and a beam homogenizer 1104. The beamhomogenizer 1104 is arranged to uniformize spatial intensities of laserbeams. Generally, the glass substrate on an X-Y stage 1109 is moved toirradiate a selected position on the substrate with a laser beam. Thelaser irradiation can be also performed by moving the optic device groupor moving the optic device group and the stage in combination.

For example, J. Im and R. Sposili describe that a substrate is mountedon an X-stage, and a homogenizer is mounted on a Y-stage in FIG. 6 of“Crystalline Si films for integrated active-matrix-liquid-crystaldisplays”, Materials Research Society Bulletin, vol. 21, (1996), p. 39(Reference 1).

Laser irradiation is also performed in vacuo or in a high purity gaseousatmosphere. Where necessary, the system has a cassette 1110 and asubstrate traveling mechanism 1111. The cassette 1110 houses glasssubstrates each with a silicon thin film, and the substrate travelingmechanism 1111 serves to move the substrate between the cassette and thestage to house the substrate in the cassette or to mount the substrateon the stage.

Japanese Patent Publication (JP-B) No. 7-118443 discloses a technique ofirradiating an amorphous silicon thin film on an amorphous substratewith a short wavelength pulse laser light. This technique cancrystallize an amorphous silicon while keeping the overall substratefrom high temperatures, and can produce semiconductor elements orsemiconductor integrated circuits on large substrates available at lowcosts. Such large substrates are required in liquid crystal displays,and such substrate available at low costs may be glasses, for example.However, as is described in the above publication, the crystallizationof an amorphous silicon thin film by action of a short wavelength laserlight requires an irradiation intensity of about 50 to 500 mJ/cm².However, the maximum emission output of a conventionally available pulselaser irradiator is at most about 1 J/pulse, and an area to beirradiated by a single irradiation is at most about 2 to 20 cm², by asimple conversion. For example, if the overall of a 47 cm×37 cmsubstrate should be crystallized by action of laser, at least 87 to 870points of the substrate must be irradiated with a laser light. Likewise,the number of points to be irradiated with a laser light increases withan increasing size of the substrate, for example, as in a 1 m×1 msubstrate. Such a laser-induced crystallization is generally performedby a pulse laser irradiator having a configuration shown in FIG. 1.

To form uniform thin film semiconductor elements on a large substrate bythe above technique, an effective process is known as disclosed inJapanese Unexamined Patent Publication (JP-A) No. 5-211167 (JapanesePatent Application No. 3-315863). The process includes the steps ofdividing the elements to portions smaller than the beam size of thelaser and repeating a combination of irradiation with several pulses andmovement of the area to be irradiated by step-and-repeat drawing method.In the process, the lasing and the movement of a stage (i.e., themovement of a substrate or laser beam) are alternatively performed, asshown in FIG. 2B. However, even according to this process, the variationof lasing intensity exceeds ±5% to ±10% when the irradiation procedureis repeated at a density of about 1 pulse per irradiated portion to 20pulses per irradiated portion using a currently available pulse laserirradiator with a uniformity of lasing intensity of ±5% to ±10% (incontinuous lasing). The resulting polycrystalline silicon thin film andpolycrystalline silicon thin film transistor cannot therefore havesatisfactorily uniform characteristics. Particularly, the generation ofa strong or weak light caused by an unstable discharge at early stagesof lasing significantly invites such heterogeneous characteristics. Thisphenomenon is called spiking. As a possible solution to the spiking, aprocess of controlling an applied voltage in a subsequent lasing withreference to the results of integrated strengths can be employed.However, according to this process, a rather weak light is oscillatedeven though the formation of spiking is inhibited. Specifically, whenirradiation periods and non-lasing periods alternatively succeed, theintensity of a first irradiated pulse in each irradiation period is mostunstable and is varied, as shown in FIG. 3. In addition, the history ofirradiation intensity differs from point to point to be irradiated. Theresulting transistor element and thin film integrated circuit cannothave a significant uniformity in the substrate plane.

To avoid such a spiking, a process is known to start lasing prior to theinitiation of irradiation to an area for the formation of element, asshown in FIG. 2A. However, this technique cannot be applied to a processof intermittently repeating the lasing and the movement of stage. Toavoid these problems, a process is proposed in Japanese UnexaminedPatent Publication (JP-A) No. 5-90191. The process includes the steps ofallowing a pulse laser source to continuously oscillate and inhibitingirradiation of a substrate with the laser light by an optic shieldingsystem during the movement of the stage. Specifically, as shown in FIG.2C, a laser is continuously oscillated at a predetermined frequency, andthe movement of stage to a target irradiation position is brought intosynchronism with the shielding of an optic path. By this configuration,a laser beam with a stable intensity can be applied to a targetirradiation position. However, although this process can stablyirradiate the substrate with a laser beam, the process also yieldsincreased excess lasing that does not serve to the formation of apolycrystalline silicon thin film. The productivity is decreased fromthe viewpoint of the life of an expensive laser source and an excitedgas, and the production efficiency of the polycrystalline silicon thinfilm is deteriorated with respect to power required for lasing. Theproduction costs are therefore increased. When a substrate to be exposedto laser is irradiated with an excessively strong light as compared witha target intensity, the substrate will be damaged. Such an excessivelystrong light is induced by an irregular irradiation intensity. In LCDsand other imaging devices, a light passing through the substratescatters in an area where the substrate is damaged, and the quality ofimage is deteriorated.

A process for reducing and projecting a pattern on a photo mask onto asilicone thin film is disclosed by R. Sposili and J. Im in “Sequentiallateral solidification of thin silicon films on SiO₂ ”, Applied PhysicsLetters, vol. 69 (1996), p. 2864 (Reference 2), and by J. Im, R.Sposili, and M. Crowder in “Single-crystal Si films for thin filmtransistor devices”, Applied Physics Letters, vol. 70, (1997), p.3434(Reference 3). The process disclosed in these publications performs anabout 1:5 reduction projection alignment using a 308-nm excimer laser, avariable-energy attenuator, a variable-focus field lens, apatterned-mask, a two-element imaging lens, and asub-micrometer-precision translation stage. By this configuration, theprocess attains a beam size and a travel pitch of a substrate stage,both of the order of micrometers. However, a laser beam applied onto thephoto mask has a spatial intensity profile depending on the lightsource, and when the process is applied to the processing of a largesubstrate as mentioned above, the strength of a patterned light passingthrough the center of the mask and that passing through the periphery ofthe mask critically differ from each other. Accordingly, a crystallinesilicon thin film having a desired uniformity cannot be significantlyobtained. In addition, as an ultraviolet radiation with a shortwavelength is reduced and projected, the focal depth of the beam issmall and the irradiation depth is liable to shift due to warp ordeformation of the substrate. With an increasing area of the substrate,the mechanical precision of the stage cannot be significantly ensured,and a little tilt of the stage or a displacement of the substrate on thestage disturbs a target laser irradiation.

A process is known for the laser irradiation. In this process, aplurality of pulses are applied while the irradiation of each pulse isretarded. This process is disclosed by Ryoichi Ishihara et al. in“Effects of light pulse duration on excimer laser crystallizationcharacteristics of silicon thin films”, Japanese Journal of AppliedPhysics, vol. 34, No. 4A, (1995), p. 1759 (Reference 4). According tothis reference, the crystallization solidification rate of a moltensilicon in a laser recrystallization process is 1 m/sec or more. Toachieve a satisfactory growth of crystals, the solidification rate mustbe reduced. By applying a second laser pulse immediately after thecompletion of solidification, the second irradiation of laser pulse canyield a recrystallization process with a reduced solidification rate. Inviewing a temperature change (a time-hysteresis curve) of silicon asshown in FIG. 4, the temperature of silicon increases with theirradiation of laser energy, for example, as a pulse with an intensityshown in FIG. 5. When a starting material is an amorphous silicon(a-Si), the temperature further increases after the melting point ofa-Si, and when the supplied energy becomes less than the energy requiredfor increasing the temperature, the material begins to undergo cooling.At the solidifying point of a crystalline Si, the solidificationproceeds for a solidification time and then completes, and the materialis cooled to an atmospheric temperature. Provided that thesolidification of silicon proceeds in a thickness direction from aninterface between silicon and the substrate, an average solidificationrate is calculated according to the following equation.Average solidification rate=(Thickness of silicon)/(Solidification time)

Specifically, if the thickness of silicon is constant, thesolidification time is effectively prolonged to reduce thesolidification rate. If the process maintains ideal conditions onthermal equilibrium, the solidification time can be prolonged byincreasing an ideally supplied energy, i.e., a laser irradiation energy.However, as pointed out in the above reference, such an increasedirradiation energy invites the resulting film to become amorphous ormicrocrystalline. In an actual melting and recrystallization process,the temperature does not change in an ideal manner as shown in FIG. 4,and the material undergoes overheating when heated and undergoessupercooling when cooled, and attains a stable condition. Particularly,when the cooling rate in cooling procedure is extremely large and thematerial undergoes an excessive supercooling, the material is notcrystallized at around its solidification point, and becomes anamorphous solid due to quenching and rapid solidification. Under someconditions, thin films are converted not into an amorphous solid butinto microcrystals, as shown in the above Reference 4. Such amicrocrystalline thin film has an extremely small grain size as comparedwith a polycrystalline thin film or a single-crystal thin film. Thus,the microcrystalline thin film includes a multitude of grain boundarieseach having a large grain boundary potential. If the thin film isapplied to, for example, a thin film transistor, the resulting thin filmtransistor will have a decreased ON-state current or an increasedOFF-state leak current.

Separately, processes are known, which include a step for the formationof a-Si thin film as a material to be irradiated with laser, a step forirradiating the thin film with a laser, a step for hydrogenation withplasma, and a step for the formation of a gate insulating film, in thisorder or in a modified order, while the material thin film is kept fromexposure to the air. These processes are disclosed in the followingpublications.

Japanese Unexamined Patent Publication No. 5-182923 discloses atechnique of subjecting an amorphous semiconductor thin film to a heattreatment and irradiating the treated thin film with a laser beam whilekeeping the thin film from exposure to the air.

Japanese Unexamined Patent Publication No. 7-99321 discloses a techniqueof moving a substrate having a laser-induced crystallizedpolycrystalline silicon thin film to a plasma-enhanced hydrogenationstep and a formation step of a gate insulating film while keeping thesubstrate from exposure to the air.

Japanese Unexamined Patent Publication No. 9-7911 discloses a techniqueof moving a substrate having a laser-induced crystallizedpolycrystalline silicon thin film to a formation step of a gateinsulating film while keeping the substrate from exposure to the air.

Japanese Unexamined Patent Publication No. 9-17729 discloses a techniqueof moving a substrate having a laser-induced crystallizedpolycrystalline silicon thin film to a formation step of a gateinsulating film while keeping the substrate from exposure to the air. Bythis configuration, the surface of the polycrystalline silicon is keptfrom adhesion of impurities.

Japanese Unexamined Patent Publication No. 9-148246 discloses atechnique of sequentially performing the formation of an amorphoussilicon thin film, laser-induced crystallization, hydrogenation, and theformation of a gate insulating film, without exposing the work to theair.

Japanese Unexamined Patent Publication No. 10-116989 discloses atechnique of sequentially performing the formation of an amorphoussilicon thin film, laser-induced crystallization, hydrogenation, and theformation of a gate insulating film, without exposing the work to theair.

Japanese Unexamined Patent Publication No. 10-149984 discloses atechnique of sequentially performing the formation of an amorphoussilicon thin film, laser-induced crystallization, hydrogenation, and theformation of a gate insulating film, without exposing the work to theair.

Japanese Unexamined Patent Publication No. 11-17185 discloses atechnique of sequentially performing the formation of an amorphoussilicon thin film, laser-induced crystallization, the formation of agate insulating film, and the formation of a gate electrode, withoutexposing the work to the air.

These concepts and techniques have been proposed to solve the followingproblems. Specifically, the surface of silicon formed by laser-inducedcrystallization is very active, and when the surface is exposed to theair, impurities are liable to adhere to the surface. Deteriorated ordispersed characteristics of the resulting TFT may therefore result.

Accordingly, the present inventors compared the performance between whenan excimer laser-induced crystallization process and a silicon oxidefilm formation process are performed in the same system (includingtransfer of the substrate to another system without exposing thesubstrate to the air) and when the film is once exposed to the air. Theresults of this experiment revealed that the former technique caninhibit adhesion of dusts and particles and therefore greatlyeffectively improves yields of products. However, by increasing levelsof cleanliness of clean room surroundings, equivalent advantages asabove can be obtained to some extent. To improve the yields, a systemincluding a film forming system and a cleaning mechanism of thesubstrate in the same system is most effective. This is becauseparticles are adhered to the substrate during film-formation under someconditions in an a-Si film forming step, and the film must be exposed tothe air to thereby be cleaned outside the system.

In contrast, differences in production processes do not significantlyaffect the performances of thin film transistors. The reasons for thismay be supposed as follows. For example, K. Yuda et al. disclose a fixedoxide film charge density (10¹¹ to 10¹² cm⁻²) of a silicon oxide filmand an interface state density (6×10¹ cm⁻² eV⁻² or less) between asilicon substrate and the silicon oxide film in “Improvement ofstructural and electrical properties in low-temperature gate-oxides forpoly-Si TFTs by controlling O₂/SiH₄ ratios”, Digest of Technical Papers1997 International Workshop on Active Matrix Liquid Crystal Displays,Sep. 11-12, 1997, Kogakuin Univ., Tokyo, Japan, 87 (Reference 5). Theabove silicon oxide film is formed at a temperature of about 300° C. to350° C. with plasma or formed through a heat treatment at about 600° C.The silicon substrate is generally subjected to an “RCA cleaning”, iswashed with water and is then introduced into a film forming system. Inthe RCA cleaning, the substrate is cleaned with an acidic solution,heated where necessary, such as a sulfuric acid-hydrogen peroxidemixture, a hydrochloric acid-hydrogen peroxide-water mixture, anammonia-hydrogen peroxide-water mixture, or a hydrofluoric acid-watermixture. The aforementioned interface state density is obtained from asample of a single-crystal silicon substrate that is exposed to the airafter the formation of a clean surface (cleaning) and is then moved tothe film-formation step.

Focusing attention to a trap state density of the laser-inducedcrystallized silicon film, H. Tanabe et al. disclose a trap statedensity of a crystallized silicon of 1012 to 1013 cm⁻² in thin filmtransistors with laser-induced crystallized silicon films, in “Excimerlaser crystallization of amorphous silicon films”, NEC Research andDevelopment, vol. 35, (1994), 254 (Reference 6). These transistorsexhibit satisfactory properties of a field effect mobility of 40 to 140cm²/Vsec.

The trap state density of the silicon film is significantly larger thanthe interface state density (or fixed oxide film charge density) of thesilicon film. Specifically, to obtain satisfactorily advantages of aclean surface of a sample that is obtained by forming a silicon film anda gate insulating film in the same system without exposing the substrateto the air, the performance (the trap state density) of the silicon filmis still insufficient.

As a means for reducing damage by plasma and forming a gate insulatingfilm of good quality, a remote plasma-enhanced chemical vapor deposition(CVD) process has been proposed. For example, Japanese Unexamined PatentPublication (JP-A) No. 5-21393 discloses a configuration in which aplasma generating chamber is separated from a substrate processingchamber. This configuration is supposed to attain such a low fixed oxidefilm charge density of 10¹¹ to 10¹² cm² and a low interface statedensity of 6×10¹⁰ cm⁻²eV⁻² or less as mentioned above. However, thisadvantage is restricted by the performances of a silicon film which ispreviously formed.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is to provide a process forforming a semiconductor thin film with a reduced trap state density bylight irradiation and to provide a process and system for applying theabove process to large substrates with a high reproducibility.

Another object of the invention is to provide a means for forming asatisfactory gate insulating film on the semiconductor thin film of goodquality and to provide a system for producing a field effect transistorhaving a satisfactory semiconductor-insulating film interface, i.e.,satisfactory properties.

(1) The invention provides, in a first aspect, a semiconductor thin filmforming system for modifying a predetermined region of a semiconductorthin film by exposing the semiconductor thin film to a projected lightpatterned through plural patterns formed on a photo mask. The systemincludes a mechanism for uniformizing the light to be applied in such amanner that the intensity of the light in a predetermined area on thephoto mask distributes within a range of ±11.2% of the average intensityof the light in the area. According to the configuration, the exposurelight is uniformized to a spatial uniformity of about ±11.2% or lesswith, for example, a beam homogenizer and is then applied onto the photomask. At least the spatial distribution of peak intensity of the lightprojected and applied on the semiconductor thin film is uniformized toan identical extent with that of the intensity distribution on the photomask. As a result, the overall exposed regions of the semiconductor thinfilm can be modified by laser irradiation in a desired manner.

(2) In a second aspect, the invention provides a semiconductor thin filmforming system for modifying a predetermined region of a semiconductorthin film by exposing the semiconductor thin film to a projected lightpatterned through an exposure pattern formed on a photo mask, and thesemiconductor thin film is formed on a substrate held on a substratestage. The system includes a mechanism for sequentially scanning thesemiconductor thin film with the patterned light by individually orconcurrently driving the photo mask and the substrate stage. When anarea on the substrate projected and irradiated with the light throughthe photo mask has a size smaller than that of the substrate, thesubstrate is moved to an irradiation area by action of the substratestage. A mask stage is moved with response to the irradiation of a laserbeam while the substrate is fixed, and target regions of the thin filmcan be sequentially exposed to light.

(3) The invention provides, in a third aspect, a semiconductor thin filmforming system for modifying a predetermined region of a semiconductorthin film by exposing the semiconductor thin film to a projected lightpatterned through an exposure pattern formed on a photo mask. The systemincludes a focusing mechanism for obtaining the focus of the patternedlight on the predetermined region of the semiconductor thin film whenthe semiconductor thin film is exposed to the projected patterned light.When the substrate is moved to an irradiated area by action of thesubstrate stage, the focus may be shifted and the focal position maydiffer between the center and the periphery of the substrate. The shiftis caused by warp, deformation of the substrate, variation of thickness,or variation of the degree of verticality of the substrate stagerelative to the exposure axis. Even in this case, the aboveconfiguration can adjust the focus as the need arises, and can provideexposure all over the substrate in a desired manner with a goodreproducibility.

(4) According to a fourth aspect, the invention provides a semiconductorthin film forming system for modifying a predetermined region of asemiconductor thin film by exposing the semiconductor thin film to aprojected exposure beam patterned through a pattern formed on a photomask. The system includes a tilt correcting mechanism (or a levelingmechanism) for correcting the tilt of the projected patterned beamrelative to the semiconductor thin film. When the substrate is moved toan irradiated area by action of the substrate stage, the focal axis maybe shifted and differ between the center and the periphery of thesubstrate. This shift is caused by warp, deformation of the substrate,variation of thickness, or variation of the degree of verticality of thesubstrate stage relative to the exposure axis. Even in this case, theabove configuration can correct the tilt or level of the substrate asthe need arises, and can provide exposure all over the substrate in adesired manner with a good reproducibility.

(5) The invention provides, in a fifth aspect, a semiconductor thin filmforming system for modifying a predetermined region of a semiconductorthin film by exposing the semiconductor thin film to a projectedexposure beam patterned through a pattern formed on a photo mask. Thesystem includes an alignment mechanism (or an alignment function) foraligning the patterned exposure beam relative to a mark formed on asubstrate, on which the semiconductor thin film is deposited. Byspecifying an exposure area with reference to the alignment markpreviously formed, a semiconductor thin film can be exposed and modifiedin a target region under target exposure conditions. For example, achannel region of a transistor alone can be exposed and modified.Specifically, source-drain and channel regions can be sequentiallypatterned and formed according to the modified regions in successivesteps.

(6) In a sixth aspect, the invention provides a semiconductor thin filmforming system for modifying a predetermined region of a semiconductorthin film by exposing the semiconductor thin film to a projected lightpatterned through a pattern formed on a photo mask. The system includesa mechanism (or a function) for holding a substrate on a stage, thesemiconductor thin film being deposited on the substrate. When an areaon the substrate projected and irradiated with the light through thephoto mask has a size smaller than that of the substrate, the substrateis moved to an irradiated area by action of the substrate stage. A maskstage is moved according to the irradiation of a laser beam while thesubstrate is fixed, and target regions of the film are sequentiallyexposed to light. In this case, the substrate on the stage is displaceddue to, for example, the movement of the substrate stage. Particularlywhen a rotation correction (θ correction) is required, corrections uponthe dislocation of the substrate deteriorate throughput, and thesubstrate must be fixed and held. When the substrate is heated on thestage, the substrate warps or bends due to heating, which causes shiftof the focus or tilt of the substrate from the exposure axis. The aboveconfiguration can avoid these problems.

(7) In a seventh aspect, the invention provides a semiconductor thinfilm forming system for modifying a predetermined region of asemiconductor thin film by exposing the semiconductor thin film to aprojected exposure beam patterned through a pattern formed on a photomask. The system includes a composing mechanism for composing aplurality of laser beams into the exposure beam.

(8) In the system just mentioned above, the plurality of laser beamspreferably comprises first and second laser beams, and the composingmechanism preferably composes the first and second laser beams in such amanner that the second laser beam is applied onto the semiconductor thinfilm with a delay relative to the first laser beam.

FIG. 6 shows the relationship of the maximum cooling rate (cooling rate,K/sec) obtained by mathematical calculation with the thresholdirradiation intensity between crystallization and microcrystallization.In this case, a 75-nm silicon thin film is irradiated with an excimerlaser with a wavelength of 308 nm, and the threshold is obtained by ascanning electron microscopic (SEM) observation of the silicon thin filmafter laser irradiation. FIG. 5 shows an emission pulse shape of thelaser used in the experiment. This pulse shape exhibits a long emissiontime five times or more that of a rectangular pulse with a pulse widthof 21.4 nsec described in the Reference 6. Even a single pulseirradiation with the pulse shape in question is therefore expected toreduce the solidification rate as described in the Reference 6.

FIG. 7 shows a calculated temperature-time curve of silicon in laserrecrystallization using the pulse shape in question. Specifically, FIG.7 shows the temperature change of a silicon thin film 75 nm thick on aSiO₂ substrate when an XeCl laser having a wavelength of 308 nm isapplied at an irradiation intensity of 450 mJ/cm². About 60 nsec intothe irradiation, a second emission peak nearly completes, and thetemperature attains the maximum and then begins to decrease. In thisconnection, in the mathematical calculation, a melting-solidificationpoint of amorphous silicon is employed as the melting-solidificationpoint, and the behavior of the material around the solidification pointdiffers from that in the actual case. Particularly when a crystallizedfilm is obtained, the crystallization completes at the solidificationpoint of the crystalline silicon.

The curve has a large gradient upon the initiation of cooling, but has avery small gradient at about 100 nsec, i.e., at a third emission peak.At an elapsed time of 120 nsec, the light emission completely ceases,and the silicon is then solidified through another rapid coolingprocess. Generally, when a liquid is solidified through “quenching”which is greatly out of a thermal equilibrium process, a sufficientlylong solidification time cannot be obtained to form a crystal structure,and the resulting solid is amorphous (non-crystal).

The maximum cooling rate was estimated from a temperature-time curve ofsilicon as shown in FIG. 7. FIG. 6 shows the estimated maximum coolingrates after the completion of light emission with respect to individualirradiation intensities. The figure shows that the cooling rateincreases with an increasing irradiation intensity.

Separately, the structure of the silicon thin film after laserirradiation was observed with a scanning electron microscope. As aresult, the grain size once increased with an increasing irradiationintensity, but microcrystallization was observed at a set irradiationintensity of about 470 mJ/cm². When the film was irradiated with threelaser pulses, the grain size markedly increased even at a setirradiation intensity of about 470 mJ/cm², while a microcrystallizedregion partially remained (FIG. 8). This large increase of the grainsize differs from the behavior of the grain size in the one-pulseirradiation. In this connection, an actual irradiation intensity is 5%to 10% higher than the set level, typically in initial several pulses ofexcimer laser. The threshold intensity at which microcrystallizationoccurs can be therefore estimated as about 500 mJ/cm².

Based on these results, the cooling rate at 500 mJ/cm² as shown in FIG.6 is estimated, and microcrystallization is found to occur at a coolingrate of about 1.6×10° C./sec or more. When the film to be irradiated isan a-Si film, the microcrystallization occurs at an irradiationintensity of about 500 mJ/cm² or more. Likewise, when the film to beirradiated is a poly-Si film, the microcrystallization may occur at anirradiation intensity about 30 mJ/cm² higher than that in the a-Si atthe same cooling rate of about 1.6×10¹⁰° C./sec. By controlling thecooling rate to 1.6×10° C./sec or less, therefore, the resulting crystalcan be kept from becoming microcrystalline or amorphous and cansatisfactorily grow.

Next, the case where a delayed second laser light is irradiated with adelay relative to a first laser light will now be described. As isdescribed above, a laser light at a late light emission stage suppressesthe increase of the cooling rate, and the cooling rate after thecompletion of light emission controls the crystallization. The lastsupplied energy is supposed to initialize precedent cooling processes.Specifically, by supplying an additional energy, a precedent coolingprocess is once initialized and a solidification process is repeatedagain, even if the crystal becomes amorphous or microcrystalline in theprecedent cooling process. This is probably because the interval oflight irradiation is very short of the order of nanoseconds, and loss ofthe energy by thermal conduction to the substrate and radiation to theatmosphere is small. The energy previously supplied therefore remainsnearly as intact. In this assumption, a long time interval sufficient todissipate heat is not considered. Accordingly, by controlling thecooling rate after the completion of a second heating by theadditionally supplied energy, the crystal is expected to growsatisfactorily. As shown in FIG. 9, the cooling rate is controlled to adesired level by controlling the delay time of the second laserirradiation.

Next, the spatial intensity distribution of an irradiated beam will bedescribed below. In laser irradiation with plural slits, the spatialdistribution in a slit and the spatial intensity distribution betweenslits should be preferably constant. However, these intensities varyplus or minus several percents to plus or minus twenty percents due torestriction of designing and production of such optic devices. At worst,the intensities vary or distribute within a range of plus or minusseveral tens of percents. Such a high variation is caused by the changeof the excimer laser beam with time or consumption of the opticalsystem, or adhesion of foreign substances to the optical system. FIG. 10shows the change of the average crystal grain size d obtained from amicroscopic photograph as shown in FIG. 8. The average crystal grainsize d depends on the irradiation intensity and the number N ofirradiation times (the number of irradiated pulses), and is expressed bythe formula d=KN^(n), wherein K is a constant and n is an inclination.FIG. 10 indicates that the inclination n of the grain size changes withrespect to the number N of irradiation times changes on the border of anirradiation intensity of about 450 mJ/cm². When target productionconditions are designed based on the irradiation intensity and thenumber N of irradiation times per irradiated site, it is preferred notto concurrently employ a condition where n=¼ and a condition wheren={fraction (1/7)}, both in the spatial intensity distribution. Even ifthe intensity spatially varies, irradiation of the film should bepreferably performed in such a manner that the irradiation intensityfalls in a range of, for example, 521 to 470 mJ/cm² (a range of ±5.2% ofan average intensity of 495 mJ/cm²) or of 424 to 339 mJ/cm² (a range of+11.2% of an average intensity of 381.5 mJ/cm²). By this configuration,a laser-crystallized Si thin film exhibiting a minimized difference inaverage grain size can be obtained.

(9) In an eighth aspect, the invention provides a semiconductor thinfilm forming system having a process chamber, and the process chamberserves to modify a predetermined region of a semiconductor thin film byexposing the semiconductor thin film on a substrate to a projected lightpatterned through a pattern formed on a photo mask. The system includesa mechanism for moving the substrate from the process chamber to adifferent process chamber without exposing the substrate to theatmosphere (or the air).

(10) In the system just mentioned in (9), the different process chamberis preferably an insulating film forming chamber for the formation of aninsulating film on the substrate.

By forming a semiconductor film-gate insulating film in the same systemwithout exposing the film to the air, the trap state density of thesemiconductor thin film becomes equal to or less than the interfacestate density, and the film can be sufficiently maintained clean tothereby yield a satisfactory semiconductor-insulating film interface.

(11) In the system according to the eighth aspect, the different processchamber may be preferably a semiconductor film forming chamber for theformation of a semiconductor film on the substrate.

(12) In the system according to the eighth aspect, the different processchamber may be preferably a heat treatment chamber for treating thesubstrate with heat.

(13) Preferably, the different process chamber in the system accordingto the eighth aspect is a plasma treatment chamber for subjecting thesubstrate to a plasma treatment by treating the substrate with plasma.

(14) In the system according to the eighth aspect, the process chamberis preferably a laser treatment chamber for modifying the predeterminedregion of the semiconductor thin film by exposing the semiconductor thinfilm on the substrate to a projected laser beam patterned through thepattern formed on the photo mask. The different process chamber ispreferably another laser treatment chamber.

By these configurations, the invention can provide high-performance andmulti-functional systems for the formation of semiconductors, canprovide processes for producing thin film transistors with a highreproducibility, and can provide high-performance thin film transistors.

Specifically, the invention can provide 1) a highly stable semiconductorthin film processing system by which a cleaning process with cleaningsolutions can be eliminated, 2) a multifunctional system by which amultitude of processes can be performed in the same system to yield aspace-saving semiconductor processing system with a reduced area of theoverall facilities, and 3) a process for producing a high performancethin film transistor at low costs, which can maintain the clean surface(interface) of silicon without the use of cleaning solutions.

(15) The different process chamber in the system indicated in one of (9)to (13) preferably includes a plasma generating source for generatingplasma in a predetermined area of the different process chamber. Thesubstrate is preferably placed in an area in the different processchamber other than the predetermined area.

(16) In the preferred system indicated in (13), the different processchamber includes a plasma generating source for generating plasma in apredetermined area of the different process chamber. The differentprocess chamber serves to subject the substrate to the plasma treatmentby reacting an excited gas with a different gas. The excited gas isexcited by the plasma generated in the predetermined area. The differentgas is introduced into the different process chamber without passingthrough the predetermined area.

By the configuration where the plasma generating chamber is separatedfrom the substrate process chamber, damage induced by plasma can bereduced to yield a satisfactory gate insulating film. In addition, thetrap state density of the semiconductor thin film becomes equal to orless than the interface state density, and a satisfactorysemiconductor-insulating film interface can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional excimer laser annealer.

FIGS. 2A to 2D are timing charts showing conventional and inventedoperation procedures of laser annealing.

FIG. 3 is a diagram showing the pulse-to-pulse stability of laser pulseintensities.

FIG. 4 is a diagram showing an illustrative temperature change of asilicon film.

FIG. 5 is a diagram showing an illustrative laser pulse shape.

FIG. 6 is a diagram showing the relationship between the irradiationintensity and the cooling rate, and the cooling rate at which the filmbecomes amorphous.

FIG. 7 is an illustrative diagram of calculated temperature changes of asilicon thin film.

FIG. 8 is a diagram showing crystal forms of silicon thin filmscorresponding to individual irradiation intensities.

FIG. 9 is a diagram showing the maximum cooling rate after the supply ofa second pulse, and the cooling rate around the solidification point.

FIG. 10 is a diagram showing the relationship between the averagecrystal grain size and the process condition.

FIG. 11 is a diagram showing the overall configuration of an embodimentof the invented exposure system.

FIG. 12 is a diagram showing an embodiment (aligning process) of theinvented exposure system.

FIGS. 13A to 13E are diagrams showing an embodiment (mask projectionprocess) of the invented exposure system.

FIGS. 14A and 14B are diagrams showing embodiments (control procedures)of the invented exposure system.

FIG. 15 is a side sectional view showing the invented exposure system,transfer chamber, and plasma-enhanced CVD chamber.

FIG. 16 is a top view of the invented composite system including, forexample, an exposure system, transfer chamber, and plasma-enhanced CVDchamber.

FIG. 17 is a side sectional view of the invented plasma-enhanced CVDchamber.

FIGS. 18A to 18G2 are sectional views showing the invented process forproducing TFT.

FIGS. 19A to 19G2 are sectional views showing the invented process forproducing TFT using an alignment mark.

FIGS. 20A to 20G2 are sectional views showing the invented process forproducing TFT including the formation of an alignment mark.

FIG. 21 is a block diagram showing an embodiment of the controlprocedure for delayed pulse lasing with plural light sources accordingto the invention.

FIGS. 22A to 22D are diagrams showing an embodiment of the controlprocedure for delayed pulse lasing from plural light sources accordingto the invention.

FIG. 23 is a diagram showing the invented laser annealer including afocusing system.

FIG. 24 is a schematic diagram of the invented composite system.

FIG. 25 is an enlarged view of the bellow shown in FIG. 24.

FIG. 26 is a diagram showing the relationship between the processchamber and the vibration isolation stage shown in FIG. 24.

FIG. 27 is an enlarged view showing the configuration of the vibrationisolation stage shown in FIG. 26.

FIG. 28 is a sectional view of the invented vacuum linear actuatordriving unit.

FIG. 29 is a vertical sectional view taken along line C-C in FIG. 28.

FIG. 30 is a diagram showing the schematic configuration of the drivingunit shown in FIG. 28.

FIG. 31 is a top view of the invented mask stage driving mechanism.

FIG. 32 is a vertical sectional view taken along line B-B in FIG. 31.

FIG. 33 is a top view showing the invented stage unit including apneumatic tilt mechanism, where a stage is dismounted.

FIG. 34 is a side sectional view of a pneumatic tilt mechanism for usein the invention.

FIG. 35 is a diagram showing the process and system for eliminatingreflected light for use in the invention.

FIG. 36 is a vertical sectional view showing the configuration of anembodiment of the invented system.

FIG. 37 is an enlarged sectional view of different holes formed in apartition.

FIG. 38 is a vertical sectional view showing the configuration ofanother embodiment of the invented system.

FIG. 39 is a vertical sectional view showing the configuration of afurther embodiment of the invented system.

FIG. 40 is a block diagram showing the configuration of the inventedsilicon oxide thin film forming system.

FIG. 41 is a graph showing an illustrative change of material gassupply.

FIG. 42 is a graph showing another illustrative change of material gassupply.

FIG. 43 is a schematic side sectional view of an embodiment of theinvented thin film forming system.

FIG. 44 is a schematic side sectional view of the configuration of themodifier supply unit 8133 arranged in the transfer chamber of the systemin FIG. 43.

FIG. 45 is a diagram of an embodiment of the composite optical system ofplural beams for use in the invention.

FIG. 46 is a diagram of an embodiment of a composite optical system ofplural beams for use in the invention.

FIG. 47 is a diagram showing an embodiment of a mask stage mechanism foruse in the invention.

FIGS. 48A and 48B are diagrams showing an embodiment of a mask stagemechanism for use in the invention.

FIG. 49 is a diagram showing the system and process for precisionalignment for rectangular beams.

FIG. 50 is a diagram showing an illustrative alignment mark arrangementfor use in the invention.

FIG. 51 is a perspective view showing the arrangement of an alignmentmark.

FIG. 52 is a diagram showing the configuration of a laser annealer as anembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiments of the invention will now be illustrated in detail withreference to the drawings.

FIG. 11 shows an embodiment of the invention. Pulsed ultraviolet (UV)beams are supplied from a first excimer laser EL1 and a second excimerlaser EL2 introduced via mirrors opt3 and otp3′ and lenses opt4 to ahomogenizer opt20′. The intensity profile of the beam is adjusted in thehomogenizer so as to attain a target uniformity in a photo mask opt21,for example, an in-plane distribution of ±5%. Original beams suppliedfrom the excimer lasers may have an intensity profile or total energywhich varies pulse to pulse. The system therefore preferably includes amechanism for adjusting the spatial intensity distribution andpulse-to-pulse intensity variation on the photo mask to achieve a higheruniformity. The homogenizer generally includes a fly-eye lens or acylindrical lens. The patterned light formed by the photo mask isapplied via a reduction projection optical system opt23′ and a laserinlet window W0 onto a substrate sub0 placed in a vacuum chamber C0. Thesubstrate is mounted on a substrate stage S0, and a target region, forexample, a pattern transfer region ex0, can be exposed to the patternedlight by operating the substrate stage. In FIG. 11, the reductionprojecting optical system is illustrated, but the system can include a1:1 projecting optical system or an enlargement projecting opticalsystem. An optional region on the substrate is irradiated with thepatterned light by moving the substrate stage in X-Y direction in thefigure. The photo mask is mounted on a mask stage (not shown), and thebeam to be applied on the substrate can be controlled also by moving thephoto mask within a region capable of being exposed.

To apply a target patterned light onto the substrate under desiredconditions, a mechanism is required. An illustrative mechanism will nowbe described. As an optical axis should be delicately and preciselyadjusted, in the following example, the optical axis is once adjustedand then fixed, and the position of the substrate is adjusted to controlthe irradiation. For adjusting the position of the irradiated surface ofthe substrate relative to the optical axis, the position of the surfacein a direction of the focus (Z direction) and the verticality relativeto the optical axis must be corrected. Of the θxy tilt correctiondirection, θxz tilt correction direction, θyz tilt correction direction,X exposure region moving direction, Y exposure region moving direction,and Z focusing direction in the figure, the verticality relative to theoptical axis is corrected by adjusting in the Oxy tilt correctiondirection, θxz tilt correction direction, and θyz tilt correctiondirection. The position of the irradiated surface of the substrate iscontrolled to an appropriate position according to the focal depth ofthe optical system by adjusting the Z focusing direction.

FIG. 12 is an illustrative side sectional view of the adjustment andalignment mechanism of the substrate. The photo mask opt21, thereduction projection optical system opt23′, and the laser inlet windowW0 are arranged with respect to an exposure axis L0, as shown in thefigure. The substrate sub0 placed in a vacuum chamber C0 is mounted on aheater H0 with a substrate adhesion mechanism, and asubstrate-XYZθxyθxzθyz-stage S0′. In this embodiment, a vacuum chamberis used, but an actual light irradiation should be preferably performedin an atmosphere of, for example, an inert gas, hydrogen gas, oxygengas, or nitrogen gas. The inside of the chamber is once evacuated and isthen replaced with the above-mentioned gas. The pressure in the chambermay be around atmospheric (barometric) pressure. By using a heater witha substrate adhesion mechanism, the substrate can be heated at atemperature of from room temperature to about 400° C. in lightirradiation procedure. When the inside pressure is set around barometricpressure, the substrate can be adhered to the heater through a vacuumchucking mechanism. Accordingly, the misalignment of the substrate canbe inhibited even if the substrate stage moves in the chamber, and thesupplied substrate can be surely fixed to the substrate stage even ifthe substrate has some warp or bending. In addition, the shift of thefocal depth due to heat-induced warp or bending can be minimized.

Laser interferometers i1 and i2 make alignment of the substrate and ameasurement of the position of the substrate in Z direction, via alength measuring window W-i and a length measuring mirror opt-i. Toalign the substrate, the position of an alignment mark on the substrateis determined with an off-axis microscope m0, a microscope light sourceLm, and a microscope element opt-m. A target exposure position can bedetermined using information about the substrate position obtained fromthe laser interferometer system. In FIG. 12, the off-axis alignment isillustrated, but the invented system can also employ through-the-lensalignment or through-the-mask (through-the-reticle) alignment. In themeasurement, measurement errors can be averaged by making measurementsfrom plural measuring points and determining a linear coordinate basedon the measured data through the least square method.

FIGS. 13A to 13E show the relationship between a mask pattern and analignment mark. The mask includes a mask non-exposure area mask1 and amask exposure area mask2. For example, when an excimer laser is used asthe light source, a film that absorbs and reflects ultraviolet radiationis formed on a quartz substrate. The ultraviolet radiation passesthrough such a quartz substrate. The film is formed from, for example,aluminum, chromium, tungsten, or other metals, or is a dielectricmultilayer film, and is then patterned by photolithography and etchingprocesses to yield the mask. According to a target pattern on the mask(indicated by the white areas in FIG. 13A), a silicon film is exposed toyield exposed Si portions (Si2) in a non-exposed Si (Si1) as shown inFIGS. 13B and 13C. Where necessary, alignment and adjustment isconducted to make a mark on the mask mark1 agree with a mark on thesubstrate mark2 prior to exposure. A predetermined and designed regionon the silicon thin film can be therefore exposed. In the thin filmtransistor forming process using a silicon thin film, if the exposureprocess is a first process requiring the alignment (i.e., no alignmentmark is formed prior to the exposure process), an exposed mark mark3should be preferably formed by exposure concurrently in the exposureprocess of the silicon thin film. By this procedure, an alignment markcan be formed using an optical color difference between a-Si andcrystalline Si. By performing, for example, photolithography in asuccessive process with reference to the above alignment mark,transistors and other desired mechanisms and functions can be formed intarget regions which are exposed and modified. Subsequent to theexposure process, an Si oxide film is formed on the silicon thin filmand a target region of the silicon film is removed by etching. FIGS. 13Dand 13E show the state just mentioned above. A removed Si region (Si3)is a region where the laminated silicon film and Si oxide film areremoved by etching. In this configuration, Si oxide films (Si4 and Si5)are laminated on the non-exposed y Si (Si1) and the exposed Si (Si2). Byforming island structures including a silicon film covered with an oxidefilm as stated above, desired channel-source-drain regions of a thinfilm transistor or alignment marks necessary for successive processescan be formed. In such a transistor, elements are separated from oneanother.

FIGS. 14A and 14B are timing charts of essential control procedures. Inthe illustrative control procedure (1), the substrate is moved to atarget exposure position by operating the substrate stage. Next, theexposure position is accurately adjusted by focusing or alignmentoperation. In this procedure, the exposure position is adjusted toachieve a target predetermined accuracy of error of, for example, about0.1 μm to 100 μm. On completion of this operation, the substrate isirradiated with light. On completion of a series of these operations,the substrate is moved to a successive exposure position. On completionof irradiation of all the necessary regions on the substrate, thesubstrate is replaced with a new one, and the second substrate to betreated is subjected to a series of the predetermined operations.

In the illustrative control procedure (2), the substrate is moved to atarget exposure position by operating the substrate stage. Next, theexposure position is accurately adjusted by focusing or alignmentoperation. In this procedure, the exposure position is adjusted toachieve a target predetermined accuracy of error of, for example, about0.1 μm to 100 μm. On completion of this operation, the mask stage startsto operate. In the chart shown in FIG. 14B, the substrate is irradiatedwith light after the initiation of the mask stage operation to avoidvariation of moving steps during startup. Naturally, a region at adistance from the alignment position is to be exposed due to themovement of the stage, and an offset corresponding to the shift must bepreviously considered. To avoid unstable operations, the light sourcemay be operated prior to the light irradiation to the substrate, and thesubstrate may be irradiated with light by opening, for example, ashutter. Particularly, when an excimer laser is employed as the lightsource and lasing periods and suspension periods are repeated in turn,several tens of pulses emitted at early stages are known to beparticularly unstable. To avoid irradiation with these unstable laserpulses, the beams can be intercepted according to the operation of themask stage. On completion of irradiation of all the necessary regions onthe substrate, the substrate is replaced with a new one, and the secondsubstrate to be treated is subjected to a series of the predeterminedoperations.

In this connection, an a-Si thin film 75 nm thick was scanned with a 1mm×50 μm beam at a 0.5-μm pitch in a minor axis direction. When thescanning (irradiation) was performed using one light source at a laserirradiation intensity of the irradiated surface of 470 mJ/cm², acontinuous single-crystal silicon thin film in the scanning directionwas obtained. In addition, a beam from a second light source was appliedwith a delay time of 100 nsec to yield a laser irradiation intensity ofthe irradiated surface of 150 mJ/cm², and a continuous single-crystalsilicon thin film in the scanning direction was obtained, even at ascanning pitch of 1.0 μm. The trap state density in the crystallizedsilicon film was less than 10¹² cm^(−2.)

FIG. 15 is a side sectional view of an embodiment of the inventedsemiconductor thin film forming system. The system includes aplasma-enhanced CVD chamber C2, a laser irradiation chamber C5, and asubstrate transfer chamber C7. In the system, the substrate can betransferred via gate valves GV2 and GV5 without exposing to anatmosphere outside the system. The transfer can be performed in vacuo orin an atmosphere of an inert gas, nitrogen gas, hydrogen gas or oxygengas, in high vacuum, under reduced pressure or under pressure. In thelaser irradiation chamber, the substrate is placed on a substrate stageS5 with the aid of a chucking mechanism. The substrate stage S5 can beheated to about 400° C. In the plasma-enhanced CVD chamber, thesubstrate is placed on a substrate holder S2. The substrate holder S2can be heated to about 400° C. The figure illustrates the followingstate. A silicon thin film Si1 is formed on a glass substrate Sub0, andthe substrate is then brought into the laser irradiation chamber. Thesurface silicon thin film is modified into a crystalline silicon thinfilm Si2 by laser irradiation, and the substrate is then transferred tothe plasma-enhanced CVD chamber.

Laser beams are brought into the laser irradiation chamber in thefollowing manner. The laser beams are supplied from an excimer laser 1(EL1) and an excimer laser 2 (EL2), pass through a first beam line L1and a second beam line L2 and a laser composing optical system opt1, amirror opt11, a transmissive mirror optl2, a laser irradiation opticalsystem opt2, a homogenizer opt20, a photo mask opt21 mounted and fixedon a photo mask stage opt22, a projection optical system opt23, and alaser inlet window W1, and reach the substrate surface. In this figure,two excimer lasers are illustrated, but a different number (one or more)of light sources can be employed in the system. The light source is notlimited to the excimer laser and includes, for example, carbon gaslaser, yttrium-aluminum-garnet (YAG) laser, and other pulse lasers. Inaddition, laser pulses can be made and applied onto the substrate byusing argon laser or another continuous wave (CW) light source and ahigh speed shutter.

In the plasma-enhanced CVD chamber, a radio frequency (RF) electrode D1and a plasma confinement electrode D3 constitute a plasma generatingregion D2 at a position at a distance from a region where the substrateis placed. For example, oxygen and helium are supplied to the plasmagenerating region, and a silane gas is supplied to the substrate using amaterial gas inlet system D4. By this configuration, a silicon oxidefilm can be formed on the substrate.

FIG. 16 is a top view of another embodiment of the inventedsemiconductor thin film forming system. A substrate transfer chamber C7is respectively connected to a load-unload chamber C₁, a plasma-enhancedCVD chamber C2, a substrate heating chamber C3, a hydrogen plasmatreatment chamber C4, and a laser irradiation chamber C5 via gate valvesGV1 through GV6. Laser beams are supplied from a first beam line L1 anda second beam line L2 and are applied to the substrate surface via alaser composing optical system opt 1, a laser irradiation optical systemopt2, and a laser inlet window W1. Gas supply systems gas1 to gas7, andventilators vent1 to vent7 are connected to the individual processchambers and the transfer chamber. By this configuration, desired gasspecies can be supplied, and target process pressures can be set. Inaddition, the ventilation and degree of vacuum can be controlled.Substrates sub2 and sub6 to be processed are placed horizontally asindicated by dotted lines in the figure.

FIG. 17 is a schematic diagram of the plasma-enhanced CVD chamber C2. Aradio frequency power source RF1 supplies a radio frequency electrodeRF2 with power. As the frequency, a high frequency of 13.56 MHz or moreis suitable. Plasmas are generated between an electrode RF3 with gassupply holes, and the radio frequency electrode RF2. Radicals are formedby plasma reaction and are introduced through the gas supply holes ofthe electrode into a region where the substrate is placed. Another gasis introduced by a flat gas supply system RF4 without exposure to theplasmas, and a gas phase reaction occurs to form a thin film on thesubstrate sub2. A substrate holder S2 is designed to heat the substratefrom room temperature to about 500° C. using, for example, a heater. Asilicon oxide film can be formed by reacting oxygen radicals with silanegas. In this reaction, the ventilator vent2, the gas supply system gas2,an oxygen gas line gas21, a helium gas line gas22, a hydrogen gas linegas23, a silane gas line gas24, a helium gas line gas25, and an argongas line gas26 are used as shown in the figure. When a silicon oxidefilm was formed at a substrate temperature of 300° C., at a pressure of0.1 Torr, at an RF power of 100 W, at a silane flow rate of 10 standardcubic centimeters per minute (sccm), at an oxygen flow rate of 400 sccm,and at a helium flow rate of 400 sccm, the resulting silicon oxide filmwas found to have a satisfactory property of a fixed oxide film chargedensity of 5×10¹¹ cm⁻². A more satisfactory oxide film can be formed byincreasing the ratio of the oxygen flow rate to the silane flow rate.The plasma-enhanced CVD chamber is not limited to a parallel plate RFplasma-enhanced CVD system as stated above. The CVD process alsoincludes a CVD process under reduced pressure, a CVD process at normalpressure, or other processes without the use of plasma, as well asplasma-enhanced CVD processes using microwaves or electron cyclotronresonance effect.

Table 1 shows illustrative gas species required when the plasma-enhancedCVD system shown in FIG. 17 is used for the formation of thin filmsother than silicon oxide films. TABLE 1 Illustrative combinations of gasspecies SiO₂ Si₃N₄ Si Si Hydro- formation formation formation formationgenation gas21 O₂ N₂ gas22 He Ar Ar gas23 H₂ H₂ H₂ gas24 SiH₄ SiH₄ SiH₄gas25 He Ar Ar gas26 SiF₄

A silicon nitride Si₃N₄ film can be formed by using nitrogen N₂ orammonia with an argon Ar carrier gas, and silane SiH₄ with an argoncarrier gas. A silicon thin film can be formed by using hydrogen H₂ andsilane, or using hydrogen with an argon carrier gas and silicontetrafluoride SiF₄ with an argon carrier gas. In addition to these filmforming processes, the plasma-enhanced CVD system can perform hydrogenplasma treatments of silicon thin films or of silicon oxide films.

FIGS. 18A to 18G2 are process flow charts showing an application of theinvented semiconductor thin film forming system to a production processof thin film transistors. The process includes the following steps.

In Step A (FIG. 18A), a glass substrate sub0 is cleaned to removeorganic substances, metals, fine particles and other impurities. Ontothe cleaned glass substrate, a substrate covering film T1 and a siliconthin film T2 are sequentially formed. As the substrate covering film, asilicon oxide film is formed to a thickness of 1 μm by low pressurevapor deposition (LPCVD) process at 450° C. with silane and oxygen gasesas materials. By using the LPCVD process, the overall exterior surfaceof the substrate can be covered with a film, except for a region wherethe substrate is held (this embodiment is not shown in the figure).Alternatively, the process can employ, for example, a plasma-enhancedCVD process using tetraethoxysilane (TEOS) and oxygen as materials, anormal pressure CVD process using TEOS and ozone as materials, or theplasma-enhanced CVD process shown in FIG. 17. An effective substratecovering film includes such a material as to prevent the diffusion ofimpurities in the substrate material. Such impurities adversely affectsemiconductor elements. The substrate may comprise, for example, a glasshaving a minimized alkali metal concentration or a quartz or glasshaving a polished surface. The silicon thin film is formed to athickness of 75 nm by LPCVD at 500° C. with a disilane gas as amaterial. Under these conditions, the resulting film is to have ahydrogen atom concentration of 1 atomic percent or less, and the filmcan be prevented from, for example, roughening due to emission ofhydrogen in the laser irradiation process. Alternatively, theplasma-enhanced CVD process shown in FIG. 17 or a conventionalplasma-enhanced CVD process can be employed. In this case, a siliconthin film having a low hydrogen atom concentration can be obtained byadjusting the substrate temperature or the flow rate ratio of hydrogento silane or the flow rate ratio of hydrogen to silicon tetrafluoride.

In Step B (FIG. 18B), the substrate prepared in Step A is subjected to acleaning process to remove organic substances, metals, fine particles,surface oxide films and other unnecessary matter. The cleaned substrateis then introduced into the invented thin film forming system. Thesubstrate is irradiated with a laser beam L0 to convert the silicon thinfilm to a crystallized silicon thin film T2′. The laser-inducedcrystallization is performed in a high purity nitrogen atmosphere of99.9999% or more at a pressure of 700 Torr or more.

In Step C (FIG. 18C), after the completion of Step B, the processchamber is evacuated, and the substrate is then transferred via asubstrate transfer chamber to a plasma-enhanced CVD chamber. As a firstgate insulating film T3, a silicon oxide film is deposited to athickness of 10 nm at a substrate temperature of 350° C. from materialsilane, helium, and oxygen gases. Where necessary, the substrate is thensubjected to hydrogen plasma treatment or to heating and annealing.Steps A to C are conducted in the invented thin film forming system.

In Step D (FIG. 18D), islands composed of laminated silicon thin filmand silicon oxide film are then formed. In this step, the etching rateof the silicon oxide film should be preferably higher than that of thesilicon thin film according to etching conditions. By forming a steppedor tapered pattern section as illustrated in the figure, the gate leakis prevented, and a thin film transistor having a high reliability canbe obtained.

In Step E (FIG. 18E), the substrate is then cleaned to remove organicsubstances, metals, fine particles and other impurities, and a secondgate insulating film T4 is formed to cover the above-prepared islands.In this example, a silicon oxide film 30 nm thick is formed by the LPCVDprocess at 450° C. from material silane and oxygen gases. Alternatively,the process can employ, for example, the plasma-enhanced CVD processusing tetraethoxysilane (TEOS) and oxygen as materials, the normalpressure CVD process using TEOS and ozone as materials, or theplasma-enhanced CVD process as shown in FIG. 17. Next, an n⁺ siliconfilm 80 nm thick and a tungsten silicide film 110 nm thick are formed asgate electrodes. The n⁺ silicon film should be preferably aphosphorus-doped crystalline silicon film formed by the plasma-enhancedCVD process or LPCVD process. The work is then subjected tophotolithography and etching processes to yield a patterned gateelectrode T5.

In Step F1 or F2 (FIGS. 18F1 or 18F2), a doping region T6 or T6′ is thenformed using the gate as a mask. When a complementary metal oxidesemiconductor (CMOS) circuit is prepared, an n⁻ channel TFT requiring ann⁺ region, and a p⁻ channel TFT requiring a p⁺ region are separatelyformed. The doping technique includes, for example, ion doping whereinjected dopant ions are not subjected to mass separation, ioninjection, plasma-enhanced doping, and laser-enhanced doping. Accordingto the application of the product or the used technique for doping, thesurface silicon oxide film remains intact (FIG. 18F 2) or is removed(FIG. 18F 1) prior to doping.

In Step G1 or G2 (FIGS. 18G1 or 18G2), an interlayer insulating film T7or T7′ is deposited, and a contact hole is formed, and a metal isdeposited thereon. The work is then subjected to photolithography andetching to yield a metallic wiring T8. Such interlayer insulating filmsinclude, but are not limited to, a TEOS-based oxide film, a silicacoating film, and an organic coating film that can provide a flat film.The contact hole can be formed by photolithography and etching with ametal. Such metals include low resistant aluminum, copper, and alloysmade from these metals, as well as tungsten, molybdenum, and otherrefractory metals. The process including these steps can produce a thinfilm transistor having high performance and reliability.

FIGS. 19A to 19G2 illustrate an embodiment where an alignment mark ispreviously formed and laser irradiation is performed with reference tothe alignment mark. FIGS. 20A to 20G2 illustrate another embodimentwhere an alignment mark is formed concurrently with laser irradiation.These embodiments are based on the TFT manufacture process flow, and arebasically similar to the process shown in FIGS. 18A to 18G2. Thedistinguishable points of these embodiments are described below.

In FIG. 19A, a glass substrate sub0 is cleaned to remove organicsubstances, metals, fine particles, and other undesired matter. On thecleaned substrate, a substrate covering film T1 and a tungsten silicidefilm are sequentially formed. The work is then patterned byphotolithography and etching to form an alignment mark T9 on thesubstrate. A mark protective film T10 is formed to protect the alignmentmark, and a silicon thin film is then formed.

In FIG. 19B, upon laser light exposure, a target region is exposed tolight with reference to the alignment mark. The alignment in thesuccessive step can be performed with reference to the preformedalignment mark or to an alignment mark formed by crystallized siliconthin film patterning (not shown).

In FIG. 20B, a crystallized alignment mark T9′ is formed concurrentlywith laser irradiation to the silicon thin film. The crystallizedalignment mark is formed by utilizing a difference in modificationbetween an exposed region and a nonexposed region.

In FIG. 20D, alignment in the photolithography process is performed byusing the crystallized alignment mark T9′. The work is then subjected toan etching process to form islands composed of laminated silicon thinfilm and silicon oxide film.

FIG. 21 shows a laser annealer for heating and laser-annealing anamorphous semiconductor with synchronizing pulses. The annealer includesa laser unit 3110, a laser irradiation processing unit 3120, and amaster controller 3130. The laser unit 3110 produces laser beams withtarget wavelengths and waveforms. The laser irradiation processing unit3120 actually subjects a substrate W to processing with the laser beamfrom the laser unit 3110. The master controller 3130 generally controlsthe operations of these units. The work substrate W is made from, forexample, a glass plate. On the surface of the substrate, for example, anamorphous Si layer as an amorphous semiconductor is deposited. The laserbeam processing converts an exposed region in the amorphous Si layerinto a polycrystalline Si (poly-Si) layer.

The laser unit 3110 includes a pair of first and second lasers 3111 and3112, and a laser controller 3113. The lasers 3111 and 3112 producepulsed laser beams. The laser controller 3113 respectively controls theexcitation timings of the lasers 3111 and 3112 to produce a pair ofpulsed laser beams with an appropriate differential time, and serves asa delay controller. The first laser 3111 is a main laser, and thesubstrate W is first irradiated with a laser beam from the first laser3111. The second laser 3112 is a subsidiary laser and the substrate W isirradiated with a laser beam from the second laser 3112 after theirradiation of the first laser. Each of the laser beams from the firstand second lasers 3111 and 3112 is appropriately adjusted to have anoptimum differential time and power for the processing of the substrateW. The both pulsed laser beams PL are superimposed via a composingoptical system 3170 to yield a synchronizing pulsed beam for processing.

The laser controller 3113 comprises, for example, a computer and asignal shaping circuit. Specifically, the laser controller includes areference pulse generating circuit 3151, a delay time setting circuit3152, an arithmetic circuit 3153, a trigger pulse generating circuit3154, first and second photosensors 3161 and 3162, a pair of amplifiers3163 and 3164, and a delay time detecting circuit 3155. The referencepulse generating circuit 3151 produces a reference pulse. The delay timesetting circuit 3152 previously sets an interval of generation, i.e.,differential time, of a pair of the pulsed laser beams PL thatconstitute the synchronizing pulsed laser beam. The arithmetic circuit3153 sets the excitation timings of the first and second lasers 3111 and3112 with reference to a signal output from, for example, the delay timesetting circuit 3152, and generates a command signal corresponding tothe excitation timings. The trigger pulse generating circuit 3154receives the output of the command signal from the arithmetic circuit3153 and generates first and second trigger signals to trigger the firstand second lasers 3111 and 3112. The first and second photosensors 3161and 3162 respectively serve for high speed photoelectric conversion oflaser outputs from the first and second lasers 3111 and 3112 and serveas photodetectors. The amplifiers 3163 and 3164 respectively amplify theoutputs from the first and second photosensors 3161 and 3162. The delaytime detecting circuit 3155 receives photo detection signals from theboth amplifiers 3163 and 3164 and detects a differential time betweenthe both photo detection signals.

The delay time setting circuit 3152 sets such a differential time(hereinafter referred to as “set differential time t1” that the waveformof the synchronizing pulsed beam is optimum for the processing of thesubstrate W. The synchronizing pulsed beam is formed by superimposingthe laser beams from the first and second lasers 3111 and 3112. The setdifferential time t1 can be set by externally entering from, forexample, a keyboard or by reading out a set level previously storedaccording to the type of the substrate W.

The arithmetic circuit 3153 generates a command signal S2 correspondingto the set differential time t1 set in the delay time setting circuit3152. The arithmetic circuit 5153 also calculates a correcteddifferential time t2 from the set differential time t1 and generates acommand signal S2′ corresponding to the corrected differential time t2.The corrected differential time t2 is calculated with reference to theoutput of a measured differential time t3 from the delay time detectingcircuit 3155.

The trigger pulse generating circuit 3154 receives the command signal S2or S2′ produced from the arithmetic circuit 3153 and subjects the signalto an appropriate processing. When triggered by the reference pulse fromthe reference pulse generating circuit 3151, the trigger pulsegenerating circuit 3154 respectively generates first and second triggersignals Tr1 and Tr2 with a time delay or shift of the differential timet1 (t2) to trigger the first and second lasers 3111 and 3112.

The delay time detecting circuit 3155 cuts a pair of photodetectionsignals from the amplifiers 3163 and 3164 with a predeterminedthreshold, and detects a delay time t3 between a pair of laser beamsproduced by the first and second lasers 3111 and 3112. The delay time t3is determined with reference to a difference of start-up timings of thesignals.

Into the laser irradiation processing unit 3120, the synchronizingpulsed laser beam is launched. The synchronizing pulsed laser beam comesout from the laser unit 3110 and is composed via a composing opticalsystem 3170 including, for example, mirrors 3171 and 3172, and a halfmirror 3173. The laser irradiation processing unit 3120 comprises areduction projection optical system 3121, a stage 3122, and a stagedriving unit 3123. The reduction projection optical system 3121 convertsthe synchronizing pulsed laser beam into a beam having a target profileand energy density distribution and projects the processed beam onto thesubstrate W. The stage 3122 supports the substrate W and moves with thesubstrate W in scanning operation. The stage driving unit 3123 controlsthe operations of the stage 3122.

The operations of the laser annealer shown in FIG. 21 will beillustrated below. The master controller 3130 controls the lasercontroller 3113 to make the first and second lasers 3111 and 3112 togenerate a pair of pulsed laser beams PL with a delay time of the setdifferential time t1. Both pulsed laser beams PL are superimposed viathe composing optical system 3170 to yield a synchronizing pulsed laserbeam for processing having a predetermined waveform, and thesynchronizing pulsed laser beam is applied onto the substrate W. Thesynchronizing pulsed laser beam is triggered by the reference pulse fromthe reference pulse generating circuit 3151, and the irradiation of thesynchronizing pulsed laser beam onto the substrate W is repeated in acycle corresponding to the cycle of the reference pulse.

In this procedure, the delay time t3 produced by the delay timedetecting circuit 3155 is monitored to find a shift Δt of the actualdelay time t3 from the set differential time t1. Thus, the correcteddifferential time t2 is calculated from Δt and t1 according to thefollowing equation.t2=t1−Δt=2×t1−t3The corrected differential time t2 is set as a new set point. By thisprocedure, the pair of pulsed laser beams PL with a time delaysubstantially identical to the set differential time t1 can be generatedfrom the first and second lasers 3111 and 3112. Specifically, if a delaytime t3′ produced by the delay time detecting circuit 3155 is out of apredetermined range (upper limit and lower limit) due to responsecharacteristics or changes with time of the first and second lasers 3111and 3112, a new corrected differential time t2′ is calculated from a newshift Δt′ and t1 [t2′=t1−Δt′] and is set as a new set point. Byrepeating these procedures, the time interval of the pair of pulsedlaser beams PL constituting the synchronizing pulsed laser beam can bemaintained constant. Specifically, even if the lasers 3111 and 3112 havedifferent characteristics from each other, and the response time fromthe trigger to exciting the laser varies due to changes with time orchanges in operation conditions, a synchronizing pulsed laser beamhaving a stable waveform can be applied onto the substrate W.

FIGS. 22A to 22D are timing charts illustrating operation timings of thesystem shown in FIG. 21. FIG. 22A shows the trigger signal Tr1 producedfrom the pulse generating circuits 3151 and 3154. FIG. 22B shows thepulsed laser beam PL launched from the first pulse laser 3111. FIG. 22Cshows the trigger signal Tr2 produced via the delay time setting circuit3152 and the arithmetic circuit 3153 from the trigger pulse generatingcircuit 3154 (these circuits are referred to as “trigger delaycircuits”). FIG. 22D shows the pulsed laser beam PL launched from thesecond pulse laser 3112. As obvious from these figures, when a delaytime Ts is set in the trigger delay circuits 3154 and 3152, a desiredpulse time interval Td (=Td2−Td1+Ts+Tc) can be theoretically obtained.

Next, a system and a process for focusing will be described as anembodiment of the invention.

FIG. 23 is a diagram showing the overall configuration of a laserannealer including the focusing system according to the embodiment. Thislaser annealer serves to subject a work W to be processed to a heattreatment. The work W comprises a glass plate and a semiconductor thinfilm of, for example, amorphous Si formed on the glass plate. The laserannealer includes a laser source 3710, an irradiation optical system3720, a stage 3730, a stage driving unit 3740, and a master controller3780. The laser source 3710 produces an excimer laser and other laserlight AL for heating the semiconductor thin film. The irradiationoptical system 3720 converts the laser light AL into a line or spot andlaunches the laser beam onto the work W at a predetermined illumination,and serves as a processing optical system. The stage 3730 supports andholds the work W, is smoothly movable in the X-Y plane, and is capableof tilting around the X and Y axes. The stage driving unit 3740 is adriving means for moving or tilting the stage 3730 with the work Wmounted thereon to a necessary degree relative to, for example, theirradiation optical system 3720. The master controller 3780 generallycontrols the operations of individual components of the laser annealer.In this configuration, the stage 3730 and the stage driving unit 3740constitute a stage unit, and are housed in a chamber 3790. The chamber3790 serves to evacuate the work W and its surroundings and to adjustthe atmosphere surrounding the work W. The chamber 3790 is placed via avibration isolator 3792 on a floor.

The laser annealer further comprises, as a focusing unit, a travelingdistance measuring sensor 3750, a tiltmeter 3760, and a non-contactdisplacement gauge 3770, in addition to the stage 3730, the stagedriving unit 3740, and the master controller 3780. The travelingdistance measuring sensor 3750 detects the travel of the stage 3730 asan optical or electric signal. The tiltmeter 3760 detects the height andtilt of the stage 3730 relative to the stage driving unit 3740 asoptical or electric information. The non-contact displacement gaugedetects signals corresponding to the height and tilt of the work Wrelative to the irradiation optical system 3720.

The irradiation optical system 3720 includes a homogenizer 3720 a, amask 3720 b, and a projection lens 3720 c. The homogenizer 3720 aensures the laser light AL to have a uniform distribution. The laserlight AL is launched from the laser source 3710 via a mirror 3715 intothe homogenizer 3720 a. The mask 3720 b has a slit for throttling thelaser light AL from the homogenizer 3720 a into a predetermined beamform. The projection lens 3720 c reduces and projects the slit imagefrom the mask 3720 b onto the work W. The irradiation optical system3720 is arranged to face the work W via a process window 3790 a in thechamber 3790, and is fixed to the chamber 3790 by a member not shown.

The stage driving unit 3740 includes a tilting unit 3742 and an XY stageunit 3744. The tilting unit 3742 makes the stage 3730 tilt around the Xand Y axes. The XY stage unit 3744 allows the stage 3730 together withthe tilting unit 3742 to smoothly move in the X-Y plane. The tiltingunit 3742 comprises three supporting members 3742 a and a supportingmember driving unit 3742 b. The supporting members 3742 a each have acylinder housed in a bellow and are capable of expanding and contractingto a selected length. The supporting member driving unit 3742 b operatesthe supporting members 3742 a to expand and contract. By adjusting thelengths of the three supporting members 3742 a through the supportingmember driving unit 3742 b, the tilt and distance of the stage 3730relative to the irradiation optical system 3720 can be appropriatelyfinely adjusted. Specifically, the work W can be adjusted relative tothe irradiation optical system 3720 in the position (distance) in the Zaxis direction, tilt angle θX around the X axis, and tilt angle θYaround the Y axis. The three tiltmeters 3760 extend from the tiltingunit 3742 side to immediately below the stage 3730 and are eddy currentsensors or electrostatic capacitance sensors. The outputs from thesesensors accurately show to what degree the stage 3730 tilts relative tothe stage driving unit 3740.

The non-contact displacement gauge 3770 is a laser displacement gauge,and includes a projecting unit 3771 and a light receiving unit 3772. Theprojecting unit 3771 is a projection means for launching a detectivelight DL to a flat region as a measuring target T on the work W. Thelight receiving unit 3772 receives a regularly reflected light RL fromthe measuring target T, and produces information about the incidentposition of the regularly reflected light RL. The projecting unit 3771and the light receiving unit 3772 are arranged to face each other withthe interposition of the irradiation optical system 3720. Specifically,the projecting unit 3771 launches the detective light DL in a directioninclining at a predetermined angle relative to the optical axis of theirradiation optical system 3720. Into the light receiving unit 3772, thereflected right RL enters in a direction. This direction inclines in anopposed direction to the detective light DL at the predetermined anglerelative to the optical axis of the irradiation optical system 3720. Themaster controller 3780 also serves as an arithmetic means for obtainingmeasurements including information corresponding to the height of themeasuring target T, with reference to the information about the incidentposition detected in the light receiving unit 3772. Thus, the mastercontroller 3780 constitutes a portion of the non-contact displacementgauge 3770.

The projecting unit 3771 comprises a light source for generating thedetective light and a projecting optical system, and launches a spotbeam of the detective light DL through the process window 3790 a to themeasuring target T on the work W. The light receiving unit 3772 includesan image-forming optical system and a line sensor. The image-formingoptical system gathers the reflected light RL from the measuring targetT, and the gathered reflected light RL enters the line sensor. The linesensor extends in the X-Z plane in a direction perpendicular to theoptical axis of the reflected light RL, and detects changes of thevertical position (height) of the work W. This configuration utilizesthe fact that the height of the work W is in a linear relationship witha position detecting signal from the line sensor. However, when the workW inclines relative to the optical axis of the irradiation opticalsystem 3720, the output of the non-contact displacement gauge 3770reflects not only the vertical position (height) of but also the tilt ofthe work W. The tilt of the work W is corrected using the tilting unit3742 to bring the normal line of the work W in parallel with the opticalaxis of the irradiation optical system 3720. At this point, the threesupporting members 3742 a constituting the tilting unit 3742 areexpanded or contracted to an identical degree to adjust the distancebetween the work W and the irradiation optical system 3720. Thisprocedure will be described in detail later.

The measuring targets T1, T2, and T3 are located at apexes of a regulartriangle. Each of the measuring targets is arranged at an identicaldistance from a processing region (in the figure, the center of the workW) on the work W. By controlling the XY stage unit 3744, the detectivelight DL from the projecting unit 3771 can be sequentially launched intoeach of the measuring targets T I, T2, and T3 on the work W. When thetilt of the work W is to be corrected, the tilting unit 3742 is operatedso as to average the outputs of the light receiving unit 3772 on theindividual measuring targets T1, T2, and T3. The arrangement of themeasuring targets T1, T2, and T3, and the total number of such measuringtargets can be appropriately modified according to, for example, arequired precision. Particularly, if the work W has warp or otherdeformations on its surface, three or more measuring targets must benewly selected for each processing region to be measured in the vicinityof the processing region in question. The above-described measuringtargets T1, T2 and T3 have only to be flat surfaces, and require nospecific mark insofar as they can produce a regularly reflected light.

The operations of the laser annealer according to the present embodimentwill now be illustrated. Initially, the work W is transferred to andmounted on the stage 3730 in the laser annealer. The work W on the stage3730 is aligned relative to the irradiation optical system 3720. Theirradiation optical system 3720 serves to guide the annealing laserlight AL. Next, the mask 3720 b of the irradiation optical system 3720is moved, or the stage 3730 is appropriately moved relative to theirradiation optical system 3720. Concurrently with this procedure, thelaser light AL from the laser source 3710 is converted into a line orspot and is launched onto the work W. On the work W, an amorphous Si oranother amorphous semiconductor thin film is formed, and a desiredregion of the semiconductor is annealed and recrystallized byirradiation and scanning of the thin film with the laser light AL. Theresulting semiconductor thin film has satisfactory electriccharacteristics.

The alignment operation of the height and tilt of the work W on thestage 3730 relative to the irradiation optical system 3720 will now beillustrated in further detail. Initially, three apexes of a regulartriangle centering on a processing region of the work W are defined asthe measuring targets T1, T2, and T3. By controlling the XY stage unit3744, the work W is appropriately moved in the X-Y plane to sequentiallymove each of the measuring targets T1, T2, and T3 on the work to ameasuring point of the non-contact displacement gauge 3770. During thisprocedure, the detective light DL is launched from the projecting unit3771 into each of the measuring targets T1, T2, and T3. The reflectedlight RL from each of the measuring targets T1, T2, and T3 is convertedinto a signal corresponding to the incident position in the lightreceiving unit 3772. In the master controller 3780, measurements aboutthe heights of the individual measuring targets T1, T2, and T3 areobtained with reference to the signals about the incident positions fromthe light receiving unit 3772. The measurements obtained from the threepoints T1, T2, and T3 are supposed to include errors due to the tilt ofthe work W. In this procedure, these errors are neglected, and the tiltangles θX and θY of the work W are adjusted by the tilting unit 3742 soas to control the heights of the three points T1, T2, and T3 to anidentical level. Then, the work W is appropriately moved in the X-Yplane by the action of the XY stage unit 3744, and measurements aboutthe heights of the individual measuring targets T1, T2, and T3 on thework W are obtained. By repeating the height measuring and theadjustment of the tilt angles of the three points T1, T2, and T3 in theabove manner, tilt-induced errors in height measurements are graduallydecreased. Ultimately, when the measurements of the three points T1, T2,and T3 agree with each other, θX=0 and θY=0, i.e. the tilt of the workbecomes zero. At this stage, any one measurement of the heightsconstitutes the height of the processing region on the work W.Ultimately, the tilting unit 3742 is operated as a Z stage to move thestage 3730, i.e., the work W, up or down to a target height.

The invention is illustrated with reference to the embodiments as above,but these embodiments are not intended to limit the scope of theinvention. For example, the system can include three or more non-contactdisplacement gauges 3770. In this case, the individual non-contactdisplacement gauges 3770 are arranged to make measurements of threedifferent points on the work W concurrently. This configuration canrapidly correct the tilt of the work W without moving the work W byaction of the XY stage unit 3744.

In the above embodiment, the tilting unit 3742 is operated as the Zstage. However, the system can include an independent Z stage tocompletely separately adjust the tilt and height of the work W.

The above embodiment employs a work W comprising a glass substrate and asemiconductor thin film formed thereon. However, the work may be made ofany material insofar as the material can produce a regularly reflectedlight.

The above focusing system is installed in a laser annealer for annealingthe semiconductor layer on the work W with the laser light AL. Thefocusing system can be also applied to not only annealers forsemiconductor materials but also pulsed laser processors byappropriately modifying the configurations of, for example, the lasersource 3710 and the irradiation optical system 3720. Such pulsed laserprocessors can serve to, for example, modify, cut or weld variousmaterials.

FIG. 24 is a schematic diagram of the configuration of a compositesystem according to the invention. The illustrated system includes a CVDsystem 3910 as a primary processing unit, and a laser annealer 3920 as asecondary processing unit. The CVD system 3910 forms a film on a glasssubstrate (work), and the laser annealer 3920 subjects the film-formedglass substrate to laser annealing.

The laser annealer 3920 comprises a sealable process chamber 3921. Theprocess chamber 3921 houses a processing stage 3922 for mounting a glasssubstrate 3901 after film-formation. A ceiling of the process chamber3921 has a process window 3923 for passing a laser beam from thefollowing laser irradiating system. The upper space of the processchamber 3921 houses a frame 3924 constituting the laser irradiatingsystem 3925.

The laser irradiating system 3925 receives a laser beam produced by alaser 3926 via a reflecting mirror 3927, shapes the laser beam to have apredetermined profile and apply the shaped laser beam to focus on theglass substrate 3901. In this system, only a configuration for arectangular beam is described. Another configuration for a long beamwill be described later.

The laser irradiating system 3925 includes, for example, a mask stage3928 supporting a mask, an optical lens system 3929, and a sensor 3930as components for a rectangular beam. The sensor 3930 serves to detectthe position of focus of the beam on the glass substrate 3901 and isused for precisely adjusting the position of focus.

The laser annealer 3920 is placed on a floor 3950 via plural vibrationisolation stages as mentioned below.

The CVD system 3910 is connected to the process chamber 3921 via atransfer chamber 3970. The transfer chamber 3970 houses a substratemoving robot 3960 as a moving mechanism. Particularly, as shown in FIG.25, the process chamber 3921 is to be connected to the transfer chamber3970 with the interposition of the bellow 3971. The connection portionbetween the process chamber 3921 and the transfer chamber 3970 is aplace where the substrate moving robot 3960 holds the glass substrate inthe CVD system 3910 and delivers the substrate to the process chamber3921. To maintain the inside of the process chamber 3921 in vacuo or ata constant pressure, the connection portion must be cut off from theair, and the bellow 3971 performs this function. The transfer chamber3970 requires a gate valve mechanism to inhibit the communicationbetween the CVD system 3910 and the process chamber 3921. Such gatevalve mechanisms are well known and are not illustrated herein.

Next, the configuration of the vibration isolation stages, essentialunits of the invented vibration isolation system, will be illustratedwith reference to FIGS. 26 and 27. Each of the vibration isolationstages 3940 comprises an upper seating 4241, and an air damper 4242connected via a vibration isolation rubber 4243 to the upper seating4241. On the upper seating 4241, the process chamber 3921 is mounted. Tothe air damper 4242, compressed air is supplied from a compressor 4244via a control valve 4245. The air damper 4242 includes a piston unit4246 and a first stopper member 4247. The piston unit 4246 moves up anddown according to the supplied compressed air. The first stopper member4247 defines a lower limit position of the piston unit 4246 duringvibration.

The upper seating 4241 comprises a second stopper member 4148. Thesecond stopper member 4148 defines on-off of operations of the vibrationisolation stages 3940, and specifies an upper limit position of thevibration isolation stages 3940, specifically, an upper limit positionin a height direction of a casing which houses the air damper 4242. Thecasing which houses the air damper 4242 includes a position detector4149 for detecting a relative distance between the casing and the secondstopper member 4148. The position detector 4149 also serves to limit thedisplacement of the casing or the process chamber as follows. If theprocess chamber 3921 or the casing which houses the air damper 4242displaces to a degree exceeding a predetermined allowable range, aportion of the position detector 4149 is engaged with the second stoppermember 4148, and this engagement limits the displacement as shown inFIG. 26.

A detective signal is sent out from the position detector 4149 to acontroller 42100 as a feedback signal. The controller 42100 controls thecontrol valve 4245 with reference to the relative distance between thesecond stopper member 4148 and the position detector 4149 indicated bythe detective signal. The controller 42100 thus operates the vibrationisolation stages 3940 to eliminate the vibration of the process chamber3921.

Particularly, when the controller 42100 detects that the relativedistance becomes equal to or less than a predetermined level, forexample, such that a portion of the position detector 4149 comes incontact with the second stopper member 4148, the controller 42100 stopsthe control operation to the control valve 4245 to cease the vibrationisolation function. Contact of a portion of the position detector 4149with the second stopper member 4148 means that up-and-down movements ofthe upper seating 4241 or of the air damper 4242 exceed the allowablerange. In this connection, the second stopper member 4148 is configuredin such a manner that the position of the second stopper member in avertical direction can be changed by a screw or another adjusting means.

As is thus described, each of the vibration isolation stages 3940 has afeedback control function. According to this function, the vibrationisolation stage 3940 controls the pressure of the compressed air whichdefines the vibration isolation property to thereby eliminate vibration,when the relative distance between the second stopper member 4148 andthe position detector 4149 changes. In addition, if the up-and-downmovements of the upper seating 4241 or of the air damper 4242 exceed theallowable range, the vibration isolation stage 3940 deactivates thefeedback control function. The position of the second stopper member4148 can be adjusted up and down by hand, and a position at which thevibration isolation function is stopped can be optionally set.

Specifically, the vibration isolation stage 3940 exerts its functionfrom a point where the piston unit 4246 comes in contact with the firststopper member 4247 to a point where a portion of the position detector4149 comes in contact with the second stopper member 4148. If thedistance between these two points is set at 200 μm, the vibrationisolation stage 3940 functions within a range of up-and-down movementsof ±100 μm.

Operations in a high precision scanning with rectangular beams will nowbe described. When rectangular beams are used for processing, thevibration in the process chamber 3921 is mainly derived from vibrationthat travels from the CVD system 3910 or the floor 3950. This vibrationhas an amplitude of at most plus or minus several tens of micrometers,and the bellow 3971 does not displace to a significant degree due toscanning. To surely activate the vibration isolation function inscanning operation with a rectangular beam, the relative distancebetween the second stopper member 4148 and the position detector 4149 inthe vibration isolation stage 3940 should be set at a level somewhatgreater than an expected displacement. For example, the relativedisplacement is set at 200 μm. In this case, vibrations from the floor3950 are absorbed by the plural vibration isolation stages 3940 throughthe feedback control function, and vibrations from the CVD system 3910are absorbed by the bellow 3971.

Next, operations in a low precision scanning with long beams will bedescribed. When long beams are used for processing, the processing stage3922 in the process chamber 3921 moves, and the location of center ofgravity of the processing stage 3922 in the process chamber 3921 shifts,and the overall process stage is liable to tilt to a great degree. Ifthe tilt is small, the same vibration isolation function works as in theprocessing with rectangular beams. However, if the tilt is large, thesecond stopper member 4148 limits the function and the vibrationisolation stage 3940 stops its function. If the vibration isolationstage 3940 does not function, the process chamber 3921 and the bellow3971 integrally move, and the relative position between the processchamber 3921 and the bellow 3971 does not shift. Accordingly, the bellow3971 is not destroyed even if it undergoes large displacement. In thisconnection, the scanning precision with long beams allows largevibrations several tens of times of that in scanning with rectangularbeams, and such vibrations do not affect the scanning precision.

Subsequently, an embodiment of the mechanical configuration of theinvented vacuum linear actuator mechanism will be illustrated in detailwith reference to FIGS. 28 and 29. A configuration suitable for use in avacuum chamber for laser annealing will be described herein. Such avacuum chamber is symbolically indicated by dashed lines 43100 in FIG.30, and includes any vacuum chamber insofar as it is usable in anatmosphere at a pressure from atmospheric pressure to about 1.0×10⁻⁶Torr.

The vacuum chamber 43100 houses a stage base 4309 as a fixed base memberat the bottom. At both side ends of the stage base 4309, Y axis linearbearings 4315 and 4320 are mounted. The Y axis linear bearings 4315 and4320 extend in parallel with each other in the Y axis direction, andserve to linearly guide a Y axis base 4314 which is assembled on thesebearings. At both side ends of the Y axis base 4314, a pair of X axislinear bearings 4307 are mounted. The X axis linear bearings 4307 extendin parallel with each other in the X axis direction, and serve tolinearly guide an X axis base 4306 assembled on these bearings. To the Xaxis base 4306, a trolley 4403 is attached. The trolley 4403 supports astage 4302 including a heating heater. On the stage 4302, a work (e.g.,a glass) 4301 is placed.

The X axis base 4306 is driven by a pair of X axis linear motors 4408.The X axis linear motors 4408 are arranged on the Y axis base 4314adjacent to the X axis linear bearings 4307. The position of the X axisbase 4306 is detected by an X axis linear encoder 4410. The X axislinear encoder 4410 is arranged on the Y axis base 4314 adjacent to oneof the X axis linear motors 4408. This configuration serves to directlydrive the X axis base 4306 and to directly detect its position. Thiseliminates deterioration of precision due to backlash according toconventional technologies, and can yield quick responses.

The Y axis base 4314 is driven by two linear motors 4318 and 4323. Thelinear motors 4318 and 4323 are placed on the stage base 4309 and can beindependently controlled. The position of the Y axis base 4314 isdetected at two points opposite to each other by two linear encoders4316 and 4321. The linear encoders 4316 and 4321 are arranged on thestage base 4309 adjacent to the linear motors 4318 and 4323,respectively. This configuration also eliminates deterioration ofprecision due to backlash and can yield quick responses, as in the Xaxis. In addition, the position in the Y axis direction is detected bythe linear encoders 4316 and 4321 at two points at opposite ends of theY axis base 4314. This configuration can detect and control minuterotation of the Y axis base 4314 with reference to a difference betweenindividual measurements. The minute rotation of the Y axis base 4314means a rotation around the Z axis which is perpendicular to X- andY-axes, and is hereinafter referred to as “rotation θ around the Zaxis”.

To prevent heat irradiated by the heater of the stage 4302 fromtransferring into the X axis base 4306 and the Y axis base 4314, awater-cooled plate 4304 is arranged between the trolley 4403 and the Xaxis base 4306. The X axis base 4306 also includes a water-coolingmechanism to prevent troubles in, for example, the linear bearings, dueto radiant heat from the heater of the stage 4302. In addition, coils ofindividual linear motors evolve heat during operation of the stage.Thus, the individual linear motors include X axis motor coil coolingplates 4411 and Y axis motor coil cooling plates 4319 and 4324,respectively, and these cooling plates cool the coils of the linearmotors. Likewise, to prevent damage or deterioration of precision due tothermal deformation, the X axis linear encoder 4310 and Y axis linearencoders 4316 and 4321 include, respectively, an X axis encoder coolingplate 4412 and Y axis encoder cooling plates 4317 and 4322. These platesmaintain the encoders at constant temperatures.

The system further includes a cable guide 4413 corresponding to the Xaxis linear encoder 4410, and cable guides 4325 respectivelycorresponding to the Y axis linear encoders 4316 and 4321. These cableguides guide cables for detective signals from the X axis linear encoder4410 and the Y axis linear encoders 4316 and 4321 to a fixed unit, asthese encoders move.

An embodiment of the invented mask stage driving mechanism will beillustrated below with reference to FIGS. 31 and 32. The configurationof the stage will now be described from top to bottom in turn. The stageincludes a base plate 4601 fixed to a fixed unit not shown. The baseplate 4601 has a large round opening in the center. The base plate 4601includes a cross roller bearing 4703 mounted at the edge of the opening,and comprises a θ axis movable unit 4604 arranged on its lower surfaceside. The θ axis movable unit 4604 is rotatably arranged around the θaxis, i.e., the Z axis via the cross roller bearing 4703. The θ axismovable unit 4601 also has an opening at its center corresponding to theopening of the base plate 4601. Under the θ axis movable unit 4604, thestage includes a Y axis movable unit 4707. The Y axis movable unit 4707is movably arranged in the Y axis direction via a pair of Y axis linearbearings 4707. The Y axis linear bearings extend in parallel with eachother in the Y axis direction. The Y axis movable unit 4707 also has anopening at its center corresponding to the opening of the base plate4601.

The Y axis movable unit 4707 comprises an X axis movable unit 4610 in aspace formed for ensuring the arrangement of the Y axis linear bearings4706. Lifting air bearings 4611 and yaw-guide air bearings 4615 and 4616guide the X axis movable unit 4610 in the X axis direction. The X axismovable unit 4610 also has an opening at its center corresponding to theopening of the base plate 4601.

Specifically, the X axis movable unit 4610 is positioned between the θaxis movable unit 4604 and the Y axis movable unit 4707 and is arrangedmovably in the X axis direction via plural lifting air bearings 4611.The lifting air bearings 4611 are arranged on a surface of the Y axismovable unit 4707 facing the X axis movable unit 4610. The lifting airbearings 4611 serve to float the X axis movable unit 4610 by blowingcompressed air to the lower surface of the X axis movable unit 4610. Themechanism shown in the figures includes three lifting air bearings 4611arranged at angular intervals of 120 degrees.

The X axis movable unit 4610 is composed of a magnetic material. The Yaxis movable unit 4707 further comprises attraction magnets 4618 atplural points on the surface facing the X axis movable unit 4610. Inthis example, a total of nine magnets 4618, i.e., each three magnetsaround three lifting air bearings 4611, are arranged. In addition, the Xaxis movable unit 4610 has two edges in parallel with the X axisdirection. By using these edges, the yaw-guide air bearings 4615 and4616 arranged on the Y axis movable unit 4707 guide the X axis movableunit 4610 in the X axis direction. Each two yaw-guide air bearings 4615and 4616 are arranged for each of the edges of the X axis movable unit4610. In addition, the two yaw-guide air bearings 4616 for one edge ofthe X axis movable unit 4610 respectively include pre-load pistons 4620in combination to apply a pre-load onto the one edge. With the X axismovable unit 4610, a mask stage 4730 is combined via a boss 4710-1. Themask stage 4730 has an opening at its center and projects from the lowerside of the Y axis movable unit 4707, and has a supporting unit for amask 4714 at its bottom. The opening of the mask stage 4730 is somewhatsmaller than the opening of the base plate 4601.

The mask stage is thus configured to have three degrees of freedom inthe X, Y, and θ axes. The output axis of a θ axis driving motor 4605moves in the axial direction according to the rotation of the θ axisdriving motor 4605 to push a θ axis driving plate 4619. This operationallows the θ axis movable unit 4606 to rotate counterclockwise aroundthe Z axis relative to its center. The output axis of the θ axis drivingmotor 4605 is not fixed to the driving plate 4619. A traction spring4617 is therefore arranged between the base plate 4601 and the θ axismovable unit 4604 to apply a pre-load in a clockwise direction. Thisconfiguration prevents backlash and irregular rotation due to, forexample, friction of the cross roller bearing 4703. The rotation angleof the θ axis movable unit 4604 is determined by a hollow rotary encoder4702 to ensure its precision. The rotary encoder 4702 is combined to arotation axis 4704-1, and the rotation axis 4704-1 is mounted on the θaxis movable unit 4604 and integrally rotates therewith. Thus, therotation precision of the θ axis movable unit 4604 is ensured.

A Y axis linear motor 4608 is arranged between the edge of the θ axismovable unit 4604 and the edge of the Y axis movable unit, and drivesthe Y axis movable unit 4707 in the Y axis direction. The position ofthe Y axis movable unit 4707 is determined by a Y axis linear encoder4709 arranged in the vicinity of the Y axis linear motor 4608. An X axislinear motor 4713 drives the X axis movable unit 4610. The X axis linearmotor 4713 is arranged under the Y axis movable unit 4707, and itsmovable part is connected to the boss 4710-1 to drive the X axis movableunit 4610 and the boss 4710-1 in the X axis direction. The position ofthe X axis movable unit 4610 is determined by an X axis linear encoder4612 arranged between the lower side of the Y axis movable unit 4707 andthe boss 4710-1.

The guide mechanism of the X axis movable unit 4610 will be illustratedin further detail below. In an actual operation, a laser light isapplied onto a work (not shown) placed under the mask using the openingof the center as an optical path, while the work is scanned with thelaser light at a constant speed. The X axis movable unit 4610 thereforerequires a high trackability and alignment accuracy (registration).Accordingly, the guide mechanism of the X axis movable unit 4610 employshydrostatic bearings, and comprises two vertical (radial) and horizontalguide mechanisms. The lifting air bearings 4611 mounted on the Y axismovable unit 4707 and the guide surface of the X axis movable unit 4610constitute the hydrostatic bearing for vertical guiding. Particularly,to ensure a gap (about 5 to 10 μm) to obtain a high guide rigidity, apre-load is applied by attraction of the plural magnets 4618 mounted onthe Y axis movable unit 4707.

Generally, air bearings are fixed to a movable unit side. However, inthis mechanism, lifting air bearings 4611 are fixed not to the X axismovable unit 4610 but to the Y axis movable unit 4707 which constitutesa base for the X axis movable unit 4610. This configuration utilizes ashort stroke necessary for the X axis movable unit 4610, and reduces theweight of the X axis movable unit 4610 and decreases the number ofconnected air-supply tubes to the air bearings. Such air-supply tubesdisturb the movement of the X axis movable unit 4610.

Two pairs of the yaw-guide air bearings 4615 and 4616 mounted on the Xaxis movable unit 4610 constitute the hydrostatic bearing for horizontalguiding of the X axis movable unit 4610. These two pairs of yaw-guideair bearings 4615 and 4616 sandwich the X axis movable unit 4610. Thetwo yaw-guide air bearings 4615 are respectively supported by expandingbolts 4621. Each of the expanding bolts 4621 is mounted on the X axismovable unit 4610 and its tip is in contact with the yaw-guide airbearing 4615. By adjusting the degree of protrusion of each expandingbolt, the horizontal position of the X axis movable unit 4610 can becontrolled.

The yaw-guide air bearings 4616 are arranged in an opposite side to theyaw-guide air bearings 4615, and are supported by pre-load pistons 4620with a constant force. This configuration can maintain constanthydrostatic bearing gaps without being affected by, for example, thermaldeformation, mechanical processing precision, and assembling errors ofthe X axis movable unit 4610, the Y axis movable unit 4707, and othercomponents.

All the support points of the air bearings are spherically supported byceramic balls. Even if the parallelism between the air bearing surfaceand a counter surface is lost due to waviness, thermal deformation, andother deformation of the counter surface, such loss in parallelism canbe absorbed to some extent.

FIGS. 33 and 34 each show a schematic diagram of a stage unit for avacuum chamber including the invented pneumatic tilt mechanism. Thestage unit is placed in a vacuum chamber that can obtain vacuum orreduced pressure. In these figures, the vacuum chamber is not shown.

The invented pneumatic tilt mechanism includes a base 5102, threebellows cylinders 5104-1, 5104-2, and 5104-3, and a plate spring 5103 onthe base 5102 to support a stage 5201. The bellows cylinders arepneumatically driven. The plate spring 5103 is in the shape of a cross.The stage 5201 includes a platform on its lower side, and the center(intercept) of the plate 5103 is fixed to the platform with, forexample, bolts. Four edges of the plate spring 5103 are respectivelyfixed via supports 5202-1 to the base 5102.

Each of the bellows cylinders 5104-1, 5104-2, and 5104-3 includes apneumatic cylinder sealed by bellows. Even if the air is leaked from thepneumatic cylinder, this configuration can prevent the leaked air frommigrating into the vacuum chamber.

The pneumatic tilt mechanism allows the plate spring 5103 to support thestage 5201, and permits the bellows cylinders 5104-1, 5104-2, and 5104-3to expand and contract by supplying compressed air to the bellowscylinders 5104-1, 5104-2, and 5104-3. The pneumatic tilt mechanism thusadjusts the height and tilt of the stage 5201.

FIG. 35 illustrates the configuration of an irradiation optical system5420. A laser light AL is launched from a laser source (not shown) intoa homogenizer 5421. The homogenizer 5421 includes first to fourthcylindrical lens arrays CA1 to CA4, and a condenser lens 5521 a. Thecylindrical lens arrays CA1 to CA4 serve to independently controlvertical and horizontal beam sizes. The condenser lens 5521 a serves tocondense the laser light. The first and third cylindrical lens arraysCA1 and CA3 have a curvature in a cross section in parallel with thepaper plane, and the second and fourth cylindrical lens arrays CA2 andCA4 have a curvature in a cross section perpendicular to the paperplane.

The laser light AL is launched from the homogenizer 5421 via a turningmirror 5525 into a mask assembly 5422. The mask assembly 5422 includes amask 5522 a, a reflecting member 5522 b, and a field lens 5522 c. Themask 5522 a has a pattern on its lower surface 5580. The pattern is tobe irradiated with the laser light AL and to be applied to a work W. Thereflecting member 5522 b inhibits the laser light AL from entering theperiphery of a light transmitting region (i.e., opening) of the patternof the mask 5522 a and from causing reflected light. The field lens 5522c adjusts the pupil position. The reflecting member 5522 b is arrangedat an angle to the mask 5522 a, and a reflected light RL from an uppersurface 5581 of the reflecting member 5522 b exits in a direction out ofan optical axis OA and enters a beam damper 5526 via the field lens 5522c. The field lens 5522 c can be considered to constitute a portion ofthe homogenizer 5421.

The laser light AL passed through the mask 5522 a enters a projectionlens 5423. The projection lens 5423 reduces and projects, i.e., forms aslit image onto a processing surface of the work W. The slit image is atransmitted patterned light formed on the mask 5522 a which isilluminated by the laser light AL.

Next, a first embodiment of the CVD system according to the inventionwill be illustrated with reference to FIGS. 36 and 37. In the CVD systemshown in FIG. 36, a silicon oxide film as a gate insulating film isformed on a conventional TFT glass substrate 7111, using, preferably,silane as a material gas. A casing 7112 of the CVD system is a vacuumcasing, and the inside of the casing is maintained at a desired degreeof vacuum during film forming operation by action of an evacuatingmechanism 7113. The evacuating mechanism 7113 is connected to anevacuating port 7112 b-1 formed in the vacuum casing 7112.

The vacuum casing 7112 houses a partition 7114 at the midpoint in avertical direction. The partition 7114 is composed of a conductivematerial and is arranged in a nearly horizontal position, and has, forexample, a square plane shape. The periphery of the partition 7114 is incontact with a peripheral wall of the vacuum casing 7112. The partition7114 serves to separate the inside of the vacuum casing 7112 to twochambers, i.e., upper and lower chambers. The upper chamber forms aplasma-generating space 7115, and the lower chamber forms a film formingspace 7116. The partition 7114 has a target specific thickness, and anoverall flat form. The plane shape of the partition 7114 is similar tothe horizontal sectional shape of the vacuum casing 7112. The partition7114 has an inner space 7124.

The glass substrate 7111 is placed on a substrate supporting mechanism7117 in the film forming space 7116. The glass substrate 7111 issubstantially in parallel with the partition 7114 and is arranged insuch a manner that its film forming surface (upper surface) faces thelower surface of the partition 7114. The potential of the substratesupporting mechanism 7117 is maintained at a grounding potentialidentical to the potential of the vacuum casing 7112. The substratesupporting mechanism 7117 further includes a heater 7118 inside thereof.The heater 7118 serves to maintain the temperature of the glasssubstrate 7111 at a predetermined level.

The configuration of the vacuum casing 7112 will now be described. Thevacuum casing 7112 comprises an upper casing 7112 a and a lower casing7112 b for easier assembling of the casing. The upper casing 7112 aforms the plasma generating space 7115, and the lower casing 7112 bforms the film forming space 7116. When the upper and lower casings 7112a and 7112 b are assembled into the vacuum casing 7112, the partition7114 is interposed between both of the casings. The partition 7114 ismounted in such a manner that the periphery of the partition comes incontact with a lower insulating member 7122 of annular insulatingmembers 7121 and 7122. The annular insulating members 7121 and 7122 areinterposed between the upper casing 7112 a and an electrode 7120, whenthe electrode 7120 is arranged. This configuration separates and formsthe plasma generating space 7115 and the film forming space 7116respectively on the upper side and lower side of the partition 7114.Specifically, the partition 7114 and the upper casing 7112 a constitutethe plasma generating space 7115. In the plasma generating space 7115,the partition 7114, the upper casing 7112 a, and the plate electrode(radio frequency electrode) 7120 constitute a region where a plasma 7119is generated. The electrode 7120 is located nearly at the midpointbetween the partition 7114 and the upper casing 7112. The electrode 7120has plural holes 7120 a. The upper casing 7112 a includes the twoannular insulating members 7121 and 7122 along the side inner surfacethereof. The partition 7114 and the electrode 7120 are supported andfixed by the annular insulating members 7121 and 7122. The annularinsulating member 7121 comprises an inlet pipe 7123 to bring an oxygengas into plasma generating space 7115 from the outside. The inlet pipe7123 is connected via a mass flow controller (not shown) to an oxygengas source (not shown). The mass flow controller controls the flow rate.

The partition 7114 separates the inside of the vacuum casing 7112 intothe plasma generating space 7115 and film forming space 7116. Thepartition 7114 has a plurality of through holes 7125. The through holes7125 meet predetermined conditions and pass through the inner space 7124and are distributed. Only the through holes 7125 allow the plasmagenerating space 7115 to communicate with the film forming space 7116.The inner space 7124 formed in the partition 7114 serves to disperse thematerial gas to thereby uniformly supply the material gas to the filmforming space 7116. In addition, the lower wall of the partition 7114includes plural diffusion holes 7126 to supply the material gas to thefilm forming space 7116. The through holes 7125 and the diffusion holes7126 are respectively made so as to meet the following predeterminedconditions. To the inner space 7124, an inlet pipe 7128 is connected forbringing the material gas into the inner space 7124. The inlet pipe 7128is connected to the lateral side of the inner space 7124. The innerspace 7124 includes a uniformizing plate 7127 nearly horizontally. Theuniformizing plate 7127 has plural perforated holes 7127 a so as tohomogeneously supply the material gas from the diffusion holes 7126. Asshown in FIG. 37, the uniformizing plate 7127 separates the inner space7124 of the partition 7114 into two, upper and lower spaces 7124 a and7124 b. The material gas is supplied via the inlet pipe 7128 into theinner space 7124. By the above configuration, the material gas issupplied into the upper space 7124 a, is brought through the holes 7127a of the uniformizing plate 7127 into the lower space 7124 b, and isdiffused through the diffusion holes 7126 into the film forming space7116. The configuration can evenly supply the material gas to theoverall film forming space 7116.

FIG. 37 is an enlarged view of a portion of the partition 7114, i.e.,essential parts of the through holes 7125, the diffusion holes 7126 andthe uniformizing plate 7127. For example, the through holes 7125 have alarger diameter on the plasma generating space 7115 side, and athrottled, smaller diameter on the film forming space 7116 side.

The upper casing 7112 a includes a power supply rod 7129 on its ceiling.The power supply rod 7129 is connected to the electrode 7120, andsupplies a radio frequency power to the electrode 7120 for discharging.The electrode 7120 serves as a radio frequency electrode. The powersupply rod 7129 is thus covered with an insulator 7131 to insulate therod from other metallic parts.

A process for forming a film with the CVD system configured as abovewill be described. The glass substrate 7111 is transferred into thevacuum casing 7112 and is placed on the substrate supporting mechanism7117 by a moving robot not shown. The inside of the vacuum casing 7112is evacuated and is maintained under reduced pressure at a predetermineddegree of vacuum by the evacuating mechanism 7113. An oxygen gas is thensupplied through the inlet pipe 7123 into the plasma generating space7115 in the vacuum casing 7112. The flow rate of the oxygen gas iscontrolled by the exterior mass flow controller. The flow velocity (u)of the oxygen gas is calculated according to the following equations (1)and (2):Q _(O2)=ρ₀₂ uA  (1)P _(O2)=(ρ_(O2) RT)/M  (2)wherein Q_(O2) is the flow rate of oxygen gas, P₀₂ is the pressure ofoxygen gas, PO₂ is the density of oxygen gas, R is the gas constant, andT is the temperature.

Separately, silane as the material gas is supplied via the inlet pipe7128 into the inner space 7124 of the partition 7114. The silane is atfirst supplied into the upper space 7124 a of the inner space 7124, isuniformized through the uniformizing plate 7127, diffuses to the lowerspace 7124 b and is then supplied through the diffusion holes 7126directly into the film forming space 7116. Specifically, the silane isintroduced into the film forming space 7116 without coming in contactwith a plasma. As the heater 7118 is energized, the substrate supportingmechanism 7117 in the film forming space 7116 is held at a predeterminedtemperature in advance.

In this state, a radio frequency power is supplied through the powersupply rod 7129 to the electrode 7120. The radio frequency power causeselectric discharge to form an oxygen plasma 7119 around the electrode7120 in the plasma generating space 7115. The generation of the oxygenplasma 7119 invites the formation of radicals (excited active species)and neutral excited species.

In this configuration, the inner space of the vacuum casing 7112 isseparated into the plasma generating space 7115 and the film formingspace 7116 by the partition 7114 composed of a conductive material. Whena film is formed on the surface of the substrate 7111, in the plasmagenerating space 7115, the oxygen gas is introduced and the radiofrequency power is supplied to the electrode 7120 to form the oxygenplasma 7119. Separately, the material gaseous silane is supplied via theinner space 7124 and the diffusion holes 7126 of the partition 7114 andis directly brought into the film forming space 7116. The radicals inthe oxygen plasma 7119 generated in the plasma generating space 7115 arebrought through the plural through holes 7125 of the partition 7114 intothe film forming space 7116, and the silane is brought through the innerspace 7124 and the diffusion holes 7126 of the partition 7114 and isdirectly introduced into the film forming space 7116. The configuration(shape) of the through holes 7125 inhibits back-diffusion of thedirectly-introduced silane from the film forming space 7116 to theplasma generating space side. As is thus described, the material gaseoussilane is directly brought into the film forming space 7116 withoutcoming in direct contact with the oxygen plasma 7119, and the silane canbe prevented from vigorously reacting with the oxygen plasma. In thismanner, a silicon oxide film is formed on the surface of the substrate7111 placed in the film forming space 7116 facing the lower side of thepartition 7114.

In the above configuration, the sizes and other dimensions of the pluralthrough holes 7125 of the partition 7114 are determined so as to limitthe transfer of the oxygen gas to a target range, provided that theoxygen gas in the plasma generating space 7115 constitutes a masstransfer flow in the through holes, and that the silane in the filmforming space 7116 diffuses and moves through the through holes 7125into the plasma generating space 7115. Specifically, the dimensions aredetermined to meet the relationship uL/D>1, wherein D is the mutual gasdiffusion coefficient of the oxygen gas and silane passing through thethrough holes 7125 of the partition 7114 at a temperature T, L is thelength (characteristic length of the through holes) of a portion of thethrough holes 7125 having the minimum diameter, and u is the gas flowvelocity. The requirements in dimensions of the through holes arepreferably applied in the same manner to the diffusion holes 7126 in thepartition 7114.

The relationship uL/D>1 can be derived in the following manner. Forexample, the relationship of the oxygen and silane moving through thethrough holes 7125 is in accordance with the following formula (3),wherein ρ_(SiH4) is the density of the silane gas, u_(SiH4) is thediffusion flow velocity, and D_(SiH4-O2) is the mutual gas diffusioncoefficient. When the characteristic length of the through hole isdefined as L, the equation (3) can be approximated to the followingequation (4). By comparing both sides of the equation (4), the diffusionflow velocity of silane u_(SiH4) is expressed by −D_(SiH4-O2)/L. Whenthe oxygen flow velocity obtained according to the above equations (1)and (2) is defined as u, and the diffusion flow velocity of silane isdefined as −DSiH4-O₂/L, the ratio between absolute values of these flowvelocities, i.e., |−u/(−D_(SiH4-O2)/L) |=uL/D_(SiH4-O2) is the ratio ofthe oxygen mass transfer rate to the silane diffusion rate. The ratiouL/D_(SiH4-O2) of 1 or more means that the flow rate through convectionis larger than the flow rate through diffusion. Specifically, the ratiouL/D_(SiH4-O2) set at 1 or more means that the diffusion of silaneaffects less the transfer of the silane.ρ_(SiH4) u _(SiH4) =−D _(SiH4-O2) grad _(psiH4)  (3)ρ_(SiH4) u _(SiH4) ≅−D _(SiH4-O2)ρ_(SiH4) /L  (4)

Next, a practical example will be described below. The value calculatedaccording to the equation (4) is 11, on condition that film-formation isperformed at a temperature of the partition of 7114 of 300° C., at adiameter of the through hole 7125 in the partition 7114 of 0.5 mm, alength (L) of 3 mm of the portion having a diameter of 0.5 mm with atotal of 500 through holes 7125, at a gas flow rate of oxygen gas of 500sccm, at a pressure of the film forming space 7116 of 100 Pa. In thiscase, the mass flow of the oxygen affects the transfer of the silane gasmore satisfactorily than the diffusion of the silane gas, and the silanegas is diffused less into the plasma generating space 7115.

As thus described, the partition 7114 having a multitude of the throughholes 7125 and diffusion holes 7126 with the above characteristicsseparates and isolates the plasma generating space 7115 and the filmforming space 7116 from each other to respectively form closed chambers.The silane directly brought into the film forming space 7116 cannotsignificantly come in contact with the oxygen plasma. According to theinvented system, the silane can be prevented from vigorously reactingwith the oxygen plasma as in conventional equivalents.

Next, a second embodiment of the invented CVD system will now beillustrated with reference to FIG. 38. In FIG. 38, componentssubstantially the same as the components described in FIG. 36 have thesame reference numerals, and detailed descriptions of these componentsare not repeated herein. A characteristic configuration of the secondembodiment is that the inside of the ceiling of the upper casing 7112 aincludes a plate insulating member 7333 and the electrode 7120 isarranged below the plate insulating member 7333. The electrode 7120 is aself plate without the holes 7120 a. The electrode 7120 and thepartition 7114 constitute the plasma generating space 7115 with aparallel plate electrode configuration. Other configurations aresubstantially the same as those of the first embodiment. In addition,the operations and advantages of the CVD system according to the secondembodiment are the same as in the first embodiment.

Subsequently, a third embodiment of the invented CVD system will now beillustrated with reference to FIG. 39. In FIG. 39, componentssubstantially the same as the components described in FIG. 36 have thesame reference numerals, and detailed descriptions of these componentsare not repeated herein. The configuration of the third embodiment ischaracterized in that the annular insulating member 7122 formed insideof the side wall of the upper casing 7112 a additionally includes asecond gas inlet pipe 7423. The second gas inlet pipe 7423 brings acleaning gas from the outside into the plasma generating space 7115. Thesecond gas inlet pipe 7423 is connected via a mass flow controller (notshown) for controlling the flow rate to a cleaning gas source (notshown). When a cleaning gas is brought via the second gas inlet pipe7423 into the plasma generating space 7115 and a radio frequency poweris supplied from the radio frequency power source to the electrode 7120,a plasma is generated in the plasma generating space 7115. This plasmaserves to form radicals for use in cleaning of the film surface on thesubstrate 7111. Such cleaning gases include, for example, NF₃, ClF₃,C₂F₄, C₂F₆, H₂, O₂, N₂, F₂, Ar, and other rare gases and halide gases.Other configurations of this embodiment are the same as those in thefirst embodiment.

The gas inlet pipe 7123 and the second gas inlet pipe 7423 arecontrolled to permit the use of either one of these inlet pipes. In thepresent embodiment, initially the cleaning gas is introduced to cleanthe film surface on the substrate 7111, and the film forming gas is thenintroduced to form a gate insulating film on the film surface on thesubstrate 7111.

Specifically, the substrate 7111 having a laser-annealed film(polysilicon film) on its surface is mounted on the substrate holder7117, and the cleaning gas is then introduced via the second gas inletpipe 7423 into the plasma generating space 7115, and a radio frequencypower is supplied via the power supply rod 7129 to the electrode 7120.By this procedure, electric discharge is initiated in the plasmagenerating space 7115 to generate a cleaning gas plasma 7419. As aresult, radicals are formed in the plasma and diffuse through the pluralthrough holes 7125 of the partition 7114 into the film forming space7116. The radicals then clean the surface of the film formed on thesubstrate 7111. This configuration can remove impurities formed on thefilm surface of the substrate after laser annealing.

After the substrate cleaning process is completed to satisfypredetermined conditions, the oxygen gas is brought from the gas inletpipe 7123 into the plasma generating space 7115, and a radio frequencypower is supplied via the power supply rod 7129 to the electrode 7120.By this procedure, electric discharge is initiated in the plasmagenerating space 7115 to yield the oxygen plasma 7119. As a result,radicals are formed in the plasma and diffuse through the plural throughholes 7125 of the partition 7114 into the film forming space 7116.Concurrently with the supply of the radicals, the material gas issupplied from the inlet pipe 7128 through the partition 7114 into thefilm forming space 7116. In the film forming space 7116, the radicalsreact with the material gas to form a gate insulating film on the filmsurface on the substrate 7111.

The invented film forming system should be preferably maintained in avacuum.

Next, a process for the formation of a film using the systems accordingto embodiments of the invention will be described.

FIG. 40 is an illustration of the invented film forming system. Thenumeral 7112 in FIG. 40 is the vacuum casing shown in FIG. 36. Thevacuum casing 7112 includes the partition 7114 having a multitude ofthrough holes, the plasma generating space 7115, and the film formingspace 7116, and the partition 7114 separates the plasma generating space7115 from the film forming space 7116.

The overall system in FIG. 40 includes a film forming material gassupply unit 7512. The material gas is supplied from the film formingmaterial gas supply unit 7512 via a gas inlet path 7513 including a massflow controller (MFC) 7513 a into the inner space 7124 in the partition7114. Such material gases include SiH₄ and other silicon hydridecompounds (Si_(n)H_(2n+2), where n is an integer of 1 or more). In thefilm forming space 7116, the material gas introduced through the innerspace 7124 in the partition 7114 reacts with the radicals introducedthrough the multitude of through holes 7125 in the partition 7114, andthe material gas is decomposed to deposit a thin film of silicon oxideon the substrate transferred into the film forming chamber. Thus, a filmis formed.

A host controller 7514 functions as a controller of the flow rate of thematerial gas in an MFC 7513 a in the gas inlet path 7513. The controller7514 can control the flow rate of the material gas in the MFC 7513 a tothereby control the supply of the material gas brought into the filmforming space 7116 to a predetermined range, as described below. FIG. 41is a graph showing an illustrative change of the material gas flow ratewith the abscissa showing the time (t) and the ordinate showing the flowrate (sccm) of the material gas. In this embodiment, the controller 7514controls the flow rate of the material gas in the MFC 7513 a in such amanner that the flow rate (supply flow rate) of the introduced materialgas to the film forming space 7116 is restricted at early stages ofelectric discharge, i.e., at early stages of film formation, and is thenincreased. Next, the manner to restrict the supply rate of the materialgas will now be described.

FIG. 42 is a graph showing an illustrative control procedure of thesupply flow rate of material gas, SiH₄, with the abscissa showing thetime and the ordinate showing the supply flow rate. In the timeabscissa, times t₀, t₁, and t₂ are set. As the plasma generating gas,for example, oxygen (O₂) is employed. The time t₀ is the time when theoxygen gas is supplied into the plasma generating chamber and electricdischarge of the oxygen gas is started, i.e., the starting point of filmformation. At the time t₁, the supply of SiH₄ starts. Accordingly, SiH₄is not supplied from the time t₀ until the time t₁. From the time t₁until the time t₂, the supply flow rate of SiH₄ gradually increases withtime and reaches a constant level at the time t₂. From the time t₂, thesupply rate of SiH₄ is maintained at the constant level. By restrictingthe supply rate of the material gas at early stages of film formationincluding the initiation of electric discharge (i.e., t₀ to t₁, andaround t₁), the formation of a silicon oxide thin film containing excesssilicon at early stages of film formation can be avoided. In addition,by gradually increasing the supply rate of the material gas thereafter,the film forming period can be shortened to thereby improve practicalutility.

From the time t₁ until time t₂, the supply rate of the material gas maybe controlled to increase according to a step function, a proportionalfunction, a linear function, a quadratic function, an exponentialfunction, and other functions.

In the above embodiments, silane is employed as an example of thematerial gas. However, the material gas is not limited to silane, andTEOS and other gaseous materials can be also employed. In addition, theinvention can be applied to film formation of not only silicon oxidefilms but also silicon nitride films. The principle of the invention canbe applied to every treatment where the material gas comes in contactwith a plasma to form particles and the introduction of ions to thesubstrate adversely affects the process, and can be applied to filmformation, surface treatments, isotropic etching, and other treatments.The partition indicated in the embodiments has a dual structure, but itmay have a multilayer structure.

According to the invention as thus described, for example, when asilicon oxide film is formed on a large substrate from silane or anothermaterial gas, a vacuum casing includes a partition having plural throughholes or diffusion holes that meet predetermined conditions. Thepartition separates the inside of the vacuum casing into a plasmagenerating space and a film forming space. An active species is formedin the plasma generating space and is brought through the through holesof the partition into the film forming space. Separately, a material gasis brought through an inner space and diffusion holes of the partitionand is directly introduced into the film forming space without coming incontact with a plasma. This configuration can inhibit a vigorouschemical reaction between the material gas and the plasma to therebyinhibit the formation of particles and introduction of ions into thesubstrate.

In addition, the invented system can evenly bring the material gas, andcan evenly supply the oxygen gas radicals through the plural throughholes formed in the partition. This configuration can yield satisfactorydistributions of the radicals and silane or another material in thevicinity of the surface of the substrate to thereby effectively form afilm on a large substrate.

FIG. 43 is a side sectional view of a clustered tool type system. Thissystem includes a film forming chamber 8101, a load-lock chamber 8102,and a transfer chamber 8103. The film forming chamber 8101 serves toform a silicon oxide film as a gate insulating film on a substrate 8109.The transfer chamber 8103 includes a moving robot 8130 as a movingmeans.

The film forming chamber 8101 includes a CVD unit 8113 inside thereof.In the CVD unit 8113, a plasma is generated, and active species takenout from the plasma serve to form a silicon oxide film. Theconfiguration of transfer chamber 8103 characterizes the systemaccording to the present embodiment. As shown in FIG. 43, the transferchamber 8103 has a gas inlet system (hereinafter referred to as“pressure regulating gas inlet system”) 8132. The pressure regulatinggas inlet system 8132 brings a gas not adversely affecting the filmformation into the inside the system to regulate the inside pressure. Inthis embodiment, the pressure regulating gas inlet system 8132introduces hydrogen gas. The pressure regulating gas inlet system 8132comprises a flow regulator and a filter not shown and can introduce ahighly purified pressure regulating gas at a predetermined flow rate.

The term “gas not adversely affecting the film formation” means andincludes gases which do not adversely affect the quality of theresulting thin film. Such gases include hydrogen and other gases that donot directly affect the film formation, and gases that improve thequality of the resulting film.

The configuration where the transfer chamber 8103 includes the pressureregulating gas inlet system 8132 is based on a characteristic technicalconcept of an evacuating unit 8131 of the transfer chamber 8103.Specifically, in the system according to the present embodiment, thepressure inside the transfer chamber 8103 is maintained at a degree ofvacuum somewhat lower than that inside the film forming chamber 8101.

The evacuating unit 8131 of the transfer chamber 8103 has only toevacuate the inside of the transfer chamber to a relatively highpressure as above, and can be configured at low costs. As the evacuatingunit 8131 of the transfer chamber 8103, for example, a combination of adry pump and a mechanical booster pump can be employed. Both componentsare available at low costs.

As the evacuating unit 8131 of the transfer chamber according toconventional equivalents, a system having an exhaust speed greater thanthat in the film forming chamber 8101 is generally employed, and theinside of the transfer chamber 8103 is evacuated to a pressure lowerthan that in the film forming chamber. However, this configuration willresult in an expensive evacuating unit 8131. For example, to attain thepressure inside the film forming chamber 8101 as stated above, aturbo-molecular pump or other expensive vacuum pumps are required.Specifically, if the target pressure is 1 Pa or higher, the system canemploy a cheap dry pump and a mechanical booster pump in combination,but if the target pressure is lower than 1 Pa, a turbo-molecular pump orother expensive pumps are required. Such pumps are several times moreexpensive than the dry pump and the mechanical booster pump.

Such a relatively high target pressure inside the transfer chamber 8103can shorten the evacuation operation to thereby increase the productionefficiency of the overall system.

The system according to this embodiment is also greatly characterized inthat the transfer chamber 8103 includes a modifier supply unit 8133. Themodifier supply unit 8133 supplies a chemical species (hereinafterreferred to as “modifier”) having a modifying activity to the surface ofthe substrate 8109. This feature will now be described in detail below.

The modifier supply unit 8133 serves to supply energy to a gasintroduced by a modifying gas inlet system 8134 to form a plasma. Theconfiguration of the modifier supply unit 8133 will be illustrated withreference to FIG. 44. FIG. 44 is a schematic side sectional view of theconfiguration of the modifier supply unit 8133 in the transfer chamber8103 of the system shown in FIG. 43.

The modifier supply unit 8133 has substantially the same configurationas the system shown in FIG. 36. However, this unit has no material gasinlet system, and the partition 7114 is a plate having plural holes. Asshown in FIG. 43, the modifier supply unit 8133 is placed in thetransfer chamber 8103 in the vicinity of a gate valve 8104 c at theboundary between the film forming chamber 8101 and the transfer chamber8103, and is located above a transfer line of the substrate 8109.

The modifying gas inlet system 8134 supplies a hydrogen gas to theplasma generating space, as in the pressure regulating gas inlet system8132. The piping of the pressure regulating gas inlet system 8132 may becaused to branch to the modifier supply unit 8133. By thisconfiguration, the pressure regulating gas inlet system 8132 also servesas the modifying gas inlet system 8134.

When a radio frequency power source goes into action while the modifyinggas inlet system 8134 brings hydrogen gas into the plasma generatingspace, a plasma is generated and active hydrogen species flow outdownward. The active hydrogen species act as a modifier in thisembodiment and are supplied to the surface of the substrate to modifythe surface. For example, when the surface of the substrate 8109 isoxidized, the oxidized surface is reduced by the modifier. If thesurface has a bondable end, the active hydrogen species terminates theend to thereby chemically stabilize the surface. During the modificationprocedure, the substrate 8109 may be stopped on the transfer line or maybe continuously transferred for a higher efficiency.

A second embodiment of this type of system will be described below. Thesystem according to the second embodiment is characterized in that alaser annealing process and a gate insulating film forming process canbe continuously performed in vacuo. These processes are required for theproduction of a TFT-LCD using a polysilicon film as a channel layer. Inthe system according to the second embodiment, the transfer chamber 8103also includes the pressure regulating gas inlet system 8132, and theinside of the transfer chamber 8103 is held at a pressure that is avacuum pressure but is higher than 1 Pa and lower than that in the filmforming chamber 8101. The pressure regulating gas inlet system 8132brings a hydrogen gas into the transfer chamber 8103 as mentioned above.

According to the second embodiment, the surface of the substrate 8109 ismodified by supplying a modifier after the annealing process. Thisconfiguration plays a very important role to improve the operatingcharacteristics of the resulting TFT. A polysilicon film formed bycrystallizing an amorphous silicon film in the annealing process hasunbonded ends of silicon (dangling bonds) on its surface. If theatmosphere contains oxygen or other gases reactive with silicon duringmovement of the substrate 8109 from an annealing chamber (not shown) tothe film forming chamber 8101, such a reactive gas readily reacts withthe dangling bonds of silicon to form a contaminated region on thesurface of the polysilicon film. If such a contaminated region is formedat an interface between the polysilicon film and the gate insulatingfilm, the resulting TFT cannot have a stoichiometric composition. Thisis liable to cause defective levels and other problems that deterioratethe operating characteristics of the TFT.

The system according to the present embodiment can avoid the aboveproblems, by modifying the surface of silicon with active hydrogenspecies after the annealing process to thereby terminate the danglingbonds of silicon with hydrogen. In addition, the transfer chamber 8103is held in vacuo at a relatively high pressure but is purged withhydrogen gas. This configuration can reduce reactions of dangling bonds,if any, with contaminates and increases the tendency of the danglingbonds to react with hydrogen to thereby terminate. By these operationsand advantages, the system according to the present embodiment canmarkedly satisfactorily improve the interface between a polysilicon filmand a gate insulating film. This point constitutes a very importanttechnical point in the manufacture of polysilicon TFTs.

The supply of a modifier by the modifier supply unit plays an importantrole in modification after the annealing process. As described above,the surface of the substrate 8109 may be modified by ion injection otherthan the use of the active species. However, ion injection formodification after the annealing process causes problems. Specifically,the polysilicon film crystallized in the annealing process has arelatively weak crystal structure. Accordingly, when ions are injected,such weak bonds are readily broken to cause, for example, a roughenedsurface of the polysilicon film. As a result, the interfacialcharacteristics may be deteriorated or channel resistance may increase.

According to the present embodiment, the CVD unit 8113 is employed togenerate a plasma in a region at a distance from the surface of thesubstrate and to supply the active species. Accordingly, substantiallyno ions are injected into the surface of the substrate and the systemdoes not invite the above problems.

FIG. 45 is a diagram illustrating the configuration of the inventedlaser annealer.

The laser annealer includes a stage 3210, a pair of laser sources 3221and 3222, a composing optical system 3230, an irradiation optical system3240, a mask driving unit 3250, a stage driving unit 3260, and a mastercontroller 32100. The stage 3210 holds or supports a work W and isthree-dimensionally smoothly movable. The work W is a glass plate havingan amorphous Si and another semiconductor thin film formed on itssurface. The laser sources 3221 and 3222 respectively produce a pair oflaser beams LB1 and LB2 having different characteristics. The composingoptical system 3230 composes the laser beams LB1 and LB2 to yield acomposite light CL. The irradiation optical system 3240 converts thecomposite light CL into a linear beam AB and launches the linear beam ABonto the work W at a predetermined illumination. The mask driving unit3250 moves a mask 3242 formed in the irradiation optical system 3240 toscan the work W with the projected linear beam AB. The stage drivingunit 3260 moves the stage 3210 supporting the work W to a necessarydegree relative to, for example, the irradiation optical system 3240.The master controller 32100 generally controls the operations ofindividual units of the overall laser annealer.

Both of the pair of laser sources 3221 and 3222 are excimer lasers orother pulsed laser sources for heating the semiconductor thin film onthe work W. The laser sources 3221 and 3222 individually andindependently produce a pair of laser beams LB1 and LB2 having differentcharacteristics such as light emitting periods, peak intensities orwavelengths.

The composing optical system 3230 serves to spatially combine the pairof laser beams LB1 and LB2 from the laser sources 3221 and 3222 to formthe composite light CL, and includes a pair of knife-edge mirrors 3231and 3232 arranged in parallel with each other. Between the composingoptical system 3230 and the both laser sources 3221 and 3222, adivergent optical system 3271 and a telescopic optical system 3272 arerespectively arranged as regulators. The divergent optical system 3271serves as a regulating optical system to finely adjust the imagingposition in the optical axis direction (beam forming position) of thefirst beam LB1 from the laser source 3221. The image is formed by ahomogenizer 3241 in the irradiation optical system 3240. The telescopicoptical system 3272 serves as an afocal optical system to adjust thebeam size of the second beam LB2 from the laser source 3222 to therebymake the beam size identical to that of the first beam LB1 entered intothe composing optical system 3230.

The irradiation optical system 3240 includes a homogenizer 3241, a mask3242, and a projection lens 3243. The homogenizer 3241 once divides thecomposite light CL from the composing optical system 3230 into pluraldivided beams and converts the divided beams into rectangular beams, andhomogeneously superimposes and launches the beams onto a predeterminedplane. The mask 3242 has a slit transmitting pattern and is arranged onthe predetermined plane to shield the composite light CL. The projectionlens 3243 reduces and projects the transmitted pattern formed on themask 3242 onto the work W as a linear beam AB.

The stage driving unit 3260 drives the stage 3210 and aligns a specificregion on the work W relative to the irradiation optical system 3240.After the mask driving unit 3250 drives the mask to scan a predeterminedregion on the work W with the linear beam AB to laser-anneal thepredetermined region, the stage driving unit 3260 also aligns the mask3242 to stepwise move the mask to a region adjacent to the predeterminedregion. A position detector 3280 continuously monitors the driving ofthe stage 3210 by the stage driving unit 3260.

The operations of the system shown in FIG. 45 will now be illustrated indetail. Initially, the work W is moved to and mounted on the stage 3210of the laser annealer. The work W on the stage 3210 is then alignedrelative to the irradiation optical system 3240. While moving the mask3242 of the irradiation optical system 3240, the composite light CLobtained from the pair of laser sources 3221 and 3222 is launched as alinear beam AB onto a predetermined region on the work W. On the work W,a thin film of an amorphous semiconductor such as an amorphous Si isformed. The irradiation and scanning of the thin film with the linearbeam AB allows the predetermined region of the semiconductor to annealand recrystallize to thereby yield a semiconductor thin film havingsatisfactory electric characteristics. The laser annealing procedure isrepeated on plural predetermined regions on the work W, and thesemiconductor thin film is annealed in the plural predetermined regions.

In the above system, the composing optical system 3230 spatiallycomposes the pair of laser beams LB1 and LB2 from the pair of lasersources 3221 and 3222 to form the composite light CL. Accordingly, thepair of laser beams LB1 and LB2 can be composed with minimized loss, andthe composite light CL as a uniform rectangular beam relative to thepair of laser beams LB1 and LB2 can be formed on predetermined plane ofmask 3242, by action of the homogenizer 3241. In addition, the linearbeam AB is obtained by efficiently composing the laser beams LB1 and LB2and can perform a variety of laser annealing procedures.

FIG. 46 is a diagram illustrating the configuration of the composingoptical system 3230 and its surroundings. As is described above, thecomposing optical system 3230 includes the pair of knife-edge mirrors3231 and 3232, allows the first beam LB1 to pass through between a pairof knife edges 3231 a and 3232 a, and separates the second beam LB2 bythe aid of the pair of knife edges 3231 a and 3232 a. The divergentoptical system 3271 finely adjusts the image-forming position of thefirst beam LB1 formed by the homogenizer 3241 and constitutes an afocalsystem including a convex lens 3271 a and a concave lens 3271 b incombination. The telescopic optical system 3272 serves to adjust thebeam size of the second beam LB2 to identical to that of the first beamLB1, and constitutes an afocal system including a concave lens 3272 aand a convex lens 3272 b in combination. Between the telescopic opticalsystem 3272 and the composing optical system 3230, a turning mirror 3233is arranged to guide the second beam LB2. Separately, the compositelight CL obtained by composing the laser beams LB1 and LB2 enters thehomogenizer 3241. The homogenizer 3241 includes first to fourthcylindrical lens arrays CA1 to CA4, and a convex condenser lens 3241 a.The first and third cylindrical lens arrays CA1 and CA3 have a curvaturein a cross section in parallel with the paper plane, and the second andfourth cylindrical lens arrays CA2 and CA4 have a curvature in a crosssection perpendicular to the paper plane.

The outline of the operations will now be described below. The firstlaser beam LB1 passes through between the knife edges 3231 a and 3232 a,i.e., a central pupil region of the homogenizer 3241 including theoptical axis OA, and the second laser beam LB2 is divided by theknife-edge mirrors 3231 and 3232 into two beams and the divided secondbeams pass through the each edge of the first beam LB1, i.e., a pair ofperipheral pupil regions of the homogenizer 3241. The beams LB1 and LB2thus respectively enter the homogenizer 3241. The homogenizer 3241 hasan entrance pupil size twice that of the beam size to allow thecomposite light CL to enter the homogenizer. The condenser lens 3241 aand other lens systems have been corrected for aberration according tothe entrance pupil.

The composite light CL entered into the homogenizer 3241 is divided intoa number equal to the number of the segments constituting thecylindrical lenses by action of the first to fourth cylindrical lensarrays CA1 to CA4 to form divided secondary light sources. The lightbeams are launched from the divided secondary light sources into thecondenser lens 3241 a, and are superimposed on an irradiated surface ISat the back focus of the condenser lens 3241 a to yield uniformrectangular beams.

The divergent optical system 3271 and the telescopic optical system 3272serve to prevent differences in focal position, beam size, anduniformity of the rectangular beams formed by the homogenizer 3241.These differences are caused by beam characteristics and differencesbetween the first and second laser beams LB1 and LB2.

The former divergent optical system 3271 slightly changes the numericalaperture (NA) of the first beam LB1 launched into the homogenizer 3241to adjust the best focal position of the homogenizer 3241 and the beamsize. The latter telescopic optical system 3272 serves to adjust thebeam size of the second beam LB2 to be identical to that of the firstbeam LB1 launched into the homogenizer 3241. By these configurations,the laser beams LB1 and LB2 are respectively divided into the samenumber as one another by the cylindrical lens arrays CA1 to CA4 to yieldan identical uniformity to each other.

The operations will be illustrated in further detail below. The firstbeam LB1 enters through a beam delivery (e.g. a turning mirror) notshown into the divergent optical system 3271 for the first beam. Thedivergent optical system 3271 is a substantially 1:1 afocal system andincludes two lenses 3271 a and 3271 b. By changing the distance betweenthe two lenses 3271 a and 3271 b, the divergent optical system 3271 canslightly adjust and change the NA of the outgoing first beam LB1 fromthe divergent optical system 3271 without significantly changing thebeam size of the first beam LB1. In a practical example, the variableadjusting range of the exit NA (a beam divergence angle of the firstbeam LB1) by the divergent optical system 3271 is set to severalmilliradians. In this connection, the two lenses 3271 a and 3271 bconstitute a two-element system of convex and concave lenses, andrespectively have little power. Even if the distance between the twolenses 3271 a and 3271 b is changed, the aberration does notsignificantly change.

The exit first beam LB1 from the divergent optical system 3271 onlypasses through between the two knife-edge mirrors 3231 and 3232, i.e.,the central region of the optical axis of the homogenizer 3241. Thefirst beam LB1 passed through between the knife-edge mirrors 3231 and3232 enters the central portion (cylindrical lenses assigned to thefirst beam LB1) of the cylindrical lens array CA1 of the homogenizer3241, and is divided into a number (six in FIG. 46) equal to the numberof the cylindrical lenses. The individual divided beams are superimposedby the condenser lens 3241 a to form a uniform beam on the irradiatedsurface IS.

The second beam LB2 is launched through a beam delivery not shown intothe telescopic optical system 3272 for the second beam. The second beamLB2 launched into the telescopic optical system 3272 is magnified orreduced in the optical system to have the identical beam size with thatof the first beam LB1, and comes out of this optical system toward thecomposing optical system 3230. The second beam LB2 is divided by theknife-edge mirrors 3231 and 3232 in the composing optical system 3230into two beam portions LB2 a and LB2 b. The beam portions LB2 a and LB2b respectively pass through each side of the first beam LB1 toward thehomogenizer 3241. Both beam portions LB2 a and LB2 b enter the outerperiphery of the optical axis of the homogenizer 3241, i.e., both edgesof the cylindrical lens array CA1 (cylindrical lenses assigned to thesecond beam LB2) of the homogenizer 3241. The beam portions are thendivided into a number equal to the number of cylindrical lenses (in FIG.46, a total of six including upper three and lower three). Theindividual divided beams are superimposed by the condenser lens 3241 ato form a uniform beam on the irradiated surface IS.

In the above description, both the first and second laser beams LB1 andLB2 are to “form a uniform beam on the irradiated surface IS”. Actually,the best focal positions of both beams may differ from each otheraccording to divergence angles of exit beams from the light source andother characteristics. When the best focal positions are different, thebeam sizes are often different. The differences in characteristics ofthe first and second beams LB1 and LB2 must be neutralized. To this end,the best focal position of the second beam LB2 is determined as a trueirradiated surface IS (reference surface) and the best focal position ofthe first beam LB1 is made in agreement with the true irradiated surfaceIS. Specifically, the exit NA of the first beam LB1, i.e., the incidentNA viewed from the homogenizer 3241 is changed by the divergent opticalsystem 3271. According to the change in the incident NA viewed from thehomogenizer 3241, the best focal position of the first beam LB1 afterpassing through the homogenizer 3241 is changed. This configuration canfinely adjust the best focal position of the first beam LB1 to agreewith that of the second beam LB2. In this connection, the relationshipbetween the exit NA and the shift of the best focal position variesaccording to the lens configuration of the homogenizer 3241, anddetailed descriptions of these fine adjustments are omitted herein.

FIG. 47 is a schematic diagram illustrating the configuration of a laserannealer as an embodiment of the invented laser processing system.

This laser annealer serves to treat a work W with heat. The work Wincludes an amorphous Si or other semiconductor thin film on a glasssubstrate. The laser annealer includes a laser source 3310, anirradiation optical system 3320, and a process stage unit 3330. Thelaser source 3310 produces a laser light AL such as excimer laser forheating the semiconductor thin film. The irradiation optical system 3320converts the laser light AL into a line form (a fine rectangular form)and launches the light onto the work W at a predetermined illumination.The process stage unit 3330 supports the work W and allows the work W tosmoothly move in the X-Y plane in a translational manner and to rotatearound the Z axis.

The irradiation optical system 3320 comprises a homogenizer 3321, a maskassembly 3322, and a projection lens 3323. The homogenizer 3321 ensuresthe incident laser beam AL to have a uniform distribution. The maskassembly 3322 has a mask on which a slit is formed, and the slitthrottles the laser light passed through the homogenizer 3321 into afine rectangular beam. The projection lens 3323 reduces and projects theslit image of the mask onto the work W. Of these components, the maskassembly 3322 is exchangeably supported on a mask stage unit 3340. Themask stage unit 3340 drives the mask assembly 3322, and the maskassembly 3322 is smoothly movable in the X-Y plane and is rotatablearound the Z axis.

The process stage unit 3330 is housed in a process chamber 3350,supports the work W in the process chamber 3350 and allows the work W toappropriately move relative to the irradiation optical system 3320. Thelaser light AL is applied from the irradiation optical system 3320 via aprocess window 3350 a onto the work W, while the work W is supported inan appropriate position in the process chamber 3350.

The system includes, on each side of the projection lens 3323, aposition detector or the like. The position detector includes aprojecting unit 3361 and a light-receiving unit 3362. The projectingunit 3361 launches a detective light via the process window 3350 a intothe surface of the work W, and the light receiving unit 3362 detects areflected light from the surface of the work W. Thus, the work W on theprocess stage unit 3330 can be precisely aligned relative to theirradiation optical system 3320.

In this configuration, the mask stage unit 3340 and the projection lens3323 are suspended by and fixed to a frame 3365 extending from theprocess chamber 3350. The homogenizer 3321 is indirectly fixed to theframe 3365, but this configuration is not shown in the figure.

The mask assembly 3322 supported by the mask stage unit 3340 issuspended at the lower end of a cylindrical mounting jig 3370, isinserted into the bottom of an insertion port 3340 a formed in the maskstage unit 3340, and is fixed thereto. The mask assembly 3322 includes amask 3322 a, a reflecting member 3322 b, and a field lens 3322 c, andintegrally holds the mask 3322 a, the reflecting member 3322 b, and thefield lens 3322 c. The mask 3322 a has a slit, and the reflecting member3322 b is arranged over the mask 3322 a at an angle relative to the mask3322 a, and inhibits other optical elements from damage due to reflectedlight from the mask 3322 a. The field lens 3322 c adjusts the divergenceangle of the laser light AL launched into the mask 3322 a.

FIGS. 48A and 48B are diagrams showing the configuration of the maskstage unit 3340 and the way to support the mask assembly 3322. FIG. 48Ais a side sectional view of the mask stage unit 3340 and surroundingcomponents, and FIG. 48B is a top view of the mounting jig 3370.

The mask stage unit 3340 includes an X axis stage 3441, a Y axis stage3442, and a θ axis stage 3443. The X axis stage 3441 allows the maskassembly 3322 to move in the X axis direction in a translational manner.The Y axis stage 3442 allows the mask assembly 3322 together with the Xaxis stage 3441 to move in the Y axis direction in a translationalmanner. The θ axis stage 3443 allows the X axis stage 3441 and the Yaxis stage 3442 to rotate around the Z axis. The X axis stage 3441 isslidably connected via a slide guide 3445 to the Y axis stage 3442. TheY axis stage 3442 is rotatably connected via a bearing 3446 to the θaxis stage 3443.

The mask assembly 3322 includes a tubular mask holder body 3422 d, and atapered outer surface TP1 tapering off downward on the outer peripheryof the mask holder body 3422 d. The mask holder body 3422 d supports themask 3322 a, the reflecting member 3322 b and the field lens 3322 c. TheX axis stage 3441 has a tapered inner surface TP2 around a round openingformed at a bottom 3441 a. The tapered inner surface TP2 is adapted tofit the tapered outer surface TP1. By this configuration, if only themask assembly 3322 is inserted into the round opening at the bottom 3441a of the X axis stage 3441, the tapered outer surface TP1 fits thetapered inner surface TP2. Thus, the mask assembly 3322 can be preciselyaligned relative to the X axis stage 3441. In addition, the maskassembly 3322 is adapted to have a downward momentum by an annularfixing nut 3425. The fixing nut 3425 is screwed into the bottom 3441 aof the X axis stage 3441.

The mask assembly 3322 and the fixing nut 3425 are mounted on the bottom3441 a of the X axis stage 3441 using the mounting jig 3370. The maskassembly 3322 has a depression 3422 g which is engaged with a hook-likehanging member 3471 formed on the lower surface of the mounting jig3370, and moves up and down according to the operation of the mountingjig 3370. By this configuration, the mask assembly 3322 can be easilyand surely inserted into the round opening at the bottom 3441 a of the Xaxis stage 3441. The fixing nut 3425 also has a depression 3425 g whichis engaged with the hanging member 3471 of the mounting jig 3370, andmoves up and down according to the operation of the mounting jig 3370.By this configuration, the fixing nut 3425 is screwed from above themask assembly 3322 inserted into the bottom 3441 a of the X axis stage3441 to easily and surely fix the mask assembly 3322.

The mounting jig 3370 includes a cylindrical body 3470 a, a discsupporting member 3470 b, and a handle 3470 c. The disc supportingmember 3470 b is fixed at the bottom of the body 3470 a and supports thehanging member 3471. The handle 3470 c serves to rotate or move the body3470 a up and down together with the supporting member 3470 b. Inconsideration of, for example, convenience of operation, the handle 3470c has a grip 3473 extending in three directions, as shown in FIG. 48B.

While the mask assembly 3322 is mounted at the bottom of the mountingjig 3370, the mask assembly 3322 is inserted into an insertion port 3440a of the mask stage unit 3340. The mask assembly 3322 is then moved downto the bottom 3441 a, and at this stage, the mounting jig 3370 is turnedin a clockwise direction to separate the mask assembly 3322 from themounting jig 3370.

Next, the fixing nut 3425 is mounted onto the bottom of the mounting jig3370 in the same manner as in the mask assembly 3322, and is insertedinto the insertion port 3440 a of the mask stage unit 3340. When thefixing nut 3425 reaches the bottom, the fixing nut 3425 is turned in acounterclockwise direction to clamp to a predetermined position. Thus,the mask assembly 3322 is pressed against the bottom 3441 a at aconstant pressure applied by a coned disc spring 3425 c. In thisprocedure, the tapered outer surface TP1 in the mask holder body 3422 dcomes into intimate contact with the tapered inner surface TP2 in thebottom 3441 a, and the mask assembly 3322 can be precisely mounted ontothe mask stage unit 3340. Thereafter, the mounting jig 3370 is turned ina clockwise direction to separate the fixing nut 3425 from the mountingjig 3370, and the mounting jig 3370 alone can be taken out.

When the mask assembly 3322 is to be dismounted from the mask stage unit3340, the above-mentioned mounting procedure should be simply reversed.Specifically, the mounting jig 3370 is inserted into the insertion port3440 a of the mask stage unit 3340 to undo the fixing nut 3425, and thefixing nut 3425 is taken out. Next, the tip of the mounting jig 3370 isallowed to catch the depression 3422 g of the mask assembly 3322. Themounting jig 3370 is then slowly raised, and the mask assembly 3322together with the mounting jig 3370 can be taken out. Likewise, thedismounting of the mask 3322 a and the reflecting member 3322 b from themask assembly 3322 can be performed in a reverse manner from themounting procedure of these elements. Detailed descriptions of suchdismounting procedures are omitted herein.

By the above procedure, the mask 3322 a can be precisely mounted ontothe mask stage unit 3340. For a further precise alignment, the mask 3322a is aligned by visual observation of an alignment mark formed on themask surface with, for example, a charge-coupled device (CCD) camera notshown.

Next, a device and process for position measurement according to anembodiment of the invention will be illustrated in further detail withreference to the drawings.

FIG. 49 is a schematic diagram showing the configuration of a laserannealer including the position measuring device according to theembodiment. The laser annealer includes a laser source 3510, anirradiation optical system 3520, a stage 3530, and a stage driving unit3540. The laser source 3510 produces an excimer laser and other laserlight AL for heating an amorphous Si or another semiconductor thin filmformed on a glass plate work W. The irradiation optical system 3520converts the laser light AL into a line or spot and launches the laserlight onto the work W at a predetermined illumination. The stage 3530supports the work W, is smoothly movable in the X-Y plane and isrotatable around the Z axis. The stage driving unit 3540 serves as adriving means to move the stage 3530 supporting the work W to anecessary degree relative to, for example, the irradiation opticalsystem 3520. The irradiation optical system 3520 may comprise, forexample, a homogenizer 3520 a, a mask 3520 b, and a projection lens 3520c. The homogenizer 3520 a ensures the incident laser light AL to have auniform distribution, and the mask 3520 b has a slit for throttling thelaser light AL passed through the homogenizer 3520 a into apredetermined beam form, and the projection lens 3520 c reduces andprojects the slit image of the mask 3520 b onto the work W.

The laser annealer further includes a traveling distance measuringdevice 3550, a projecting optical system 3560, a first image pickupdevice 3571, a second image pickup device 3572, an image processor 3580,and an illumination lamp 3565, as a position measuring device inaddition to the stage 3530 and the stage driving unit 3540. Thetraveling distance measuring device 3550 detects the displacement of thestage 3530 as optical or electric information. The projecting opticalsystem 3560 is a coaxial twin-lens dual-scaling system and forms animage of an alignment mark on the work W. The first image pickup device3571 converts a first-scaling image of a relatively low magnificationprojected by the projecting optical system 3560 into a picture signal,and the second image pickup device 3572 converts a second-scaling imageof a relatively high magnification projected by the projecting opticalsystem 3560 into a picture signal. The image processor 3580 subjects thepicture signals produced by the first and second image pickup devices3571 and 3572 to an appropriate signal processing. The illumination lamp3565 supplies luminous light to the projecting optical system 3560 forthe illumination of the surface of the work W. The laser annealerfurther includes a master controller 3585 which generally controls theoperations of the position measuring device and other components of thelaser annealer.

The irradiation optical system 3560 will now be illustrated in furtherdetail. The irradiation optical system 3560 is a coaxial twin-lensdual-scaling system as described above, and includes a first lens system3561 a and 3561 b, a second lens system 3562 a and 3562 b, a half mirror3563, and an epi-illumination system 3567. The first lens system 3561 aand 3561 b projects an image of the work W on the stage 3530 onto thefirst image pickup device 3571 in a relatively low first magnification.The second lens system 3562 a and 3562 b projects this projected imagein a relatively high second magnification onto the second image pickupdevice 3572. The half mirror 3563 divides the image light IL from thework W and introduces the divided beams into the first lens system 3561a and 3561 b and the second lens system 3562 a and 3562 b. Theepi-illumination system 3567 guides an illumination light from theillumination lamp 3565 via a cable 3566 onto the optical axis of thesecond image pickup device 3572. The illumination light produced by theillumination light 3565 has a wavelength different from that of thelaser light from the laser source 3510.

The first lens system 3561 a and 3561 b and the second lens system 3562a and 3562 b constitute a coaxial optical system possessing an opticalaxis in common. The image light IL is launched from the work W along theoptical axis of the first lens system 3561 a and 3561 b. When the imagelight IL is reflected by the half mirror 3563, it enters into the centerof an image field of the first image pickup device 3571. When the imagelight IL passes through the half mirror 3563, it enters along theoptical axis of the second lens system 3562 a and 3562 b into the centerof an image field of the second image pickup device 3572. In addition,the epi-illumination system 3567 is arranged to be coaxial with thesecond lens system 3562 a and 3562 b, and homogeneously illuminates aregion on the work W corresponding to the image fields of the first andsecond image pickup devices 3571 and 3572.

The first image pickup device 3571 comprises a CCD device, a solid imagepickup device. The first image pickup device 3571 and the lens 3561 bconstitute a CCD camera 3573. The CCD camera 3573 is fixed to an end ofa lens-barrel 3575 housing the lens 3561 a. Separately, the second imagepickup device 3572 also comprises a CCD device, and the second imagepickup device 3572 and the lens 3562 b constitute a CCD camera 3574. TheCCD camera 3574 is fixed to an end of a lens-barrel 3576 housing thelens 3562 a. The other ends of the both lens-barrels 3575 and 3576 arefixed to a casing which houses the half mirror 3563.

FIG. 50 is a diagram showing an illustrative arrangement of alignmentmarks formed on the surface of the work W mounted on the stage 3530 ofFIG. 49. Alignment marks M1 and M2 shown in the figure are each a dualpattern including a bright, large cross pattern and a dark, small crosspattern in combination.

The first alignment mark M1 is formed in one of the four corners of thework W, and the second alignment mark M2 is formed at another of thefour corners of the work W. The first and second alignment marks M1 andM2 are thus formed in two positions on the work W so as to detect notonly the position but also the rotation of the work W. By measuring thepositions of the first and second alignment marks M1 and M2, thecoordinates of the two reference points on the work W can be determined,and the work W can be aligned in such a manner that the attitude andposition of the work W can be appropriately adjusted.

The operations of the laser annealer shown in FIG. 49 will be describedin detail. The work W is moved to and mounted on the stage 3530 of thelaser annealer. The work W on the stage 3530 is aligned relative to theirradiation optical system 3520 serving to guide the annealing laserlight AL. While appropriately moving the stage 3530 relative to theirradiation optical system 3520, the laser light AL is launched from thelaser source 3510 and is converted into a line or a spot and is appliedonto the work W. On the work W, an amorphous Si or another amorphoussemiconductor thin film is formed, and the semiconductor is annealed andrecrystallized by irradiation and scanning of the work with the laserlight AL. The resulting semiconductor thin film has satisfactoryelectric characteristics.

The position measuring device is used for the alignment of the work W onthe stage 3530 relative to the irradiation optical system 3520.Specifically, the stage 3530 is appropriately moved by the stage drivingunit 3540 to guide the first alignment mark M1 including a global markM11 and a fine mark M12 to an image field of the first image pickupdevice 3571 (Step S1). The position of the work W on the stage 3530remains within a predetermined moving precision range (0.5 to 1 mm inthe example), and the stage 3530 is appropriately moved relative to theprojecting optical system 3560 to guide and move the first alignmentmark M1 in the visual field of the first lens system 3561 a and 3561 b,i.e., in the image field (5 mm size in the example) of the first imagepickup device 3571. For example, by storing the position of the firstalignment mark M1 on the work W in memory as data, the stage 3530 can beappropriately moved with reference to the positional data of the firstalignment mark M1 to surely guide the first alignment mark M1 into theimage field of the first image pickup device 3571.

Subsequently, the position of the global mark M11 of the first alignmentmark M1 is determined by subjecting the picture signal of a relativelylow magnification from the first image pickup device 3571 to imagesignal processing in the image processor 3580 (Step S2). The pixels ofthe first image pickup device 3571 are in a precise correspondence withdistances of points on the stage 3530, and an XY component of thedistance from the center of the first image pickup device 3571, i.e. theoptical axis of the first lens system 3561 a and 3561 b, to the centerof the global mark M11 can be precisely determined.

Next, while determining and monitoring the travel or stroke of the stageby the traveling distance measuring device 3550, the stage driving unit3540 is driven to move the stage 3530 in the X-Y plane to allow thecenter of the global mark M11 to agree with the optical axis of thefirst lens system 3561 a and 3561 b (Step S3). The travel determined bythe travel measuring device 3550 corresponds to the distance determinedin the step S2. In this procedure, the alignment accuracy by the globalmark M11 is about 10 μm or less in the example. The above searchalignment procedure can positively move the fine mark M12 arranged atthe center of the global mark M11 into the image field (0.5 mm size inthe example) of the second image pickup device 3572 of a highmagnification.

The position of the fine mark M12 is then determined by subjecting apicture signal from the second image pickup device 3572 to signalprocessing in the image processor 3580 (Step S4). The pixels of thesecond image pickup device 3572 have a precise correspondence withdistances of points on the stage 3530, and the distance between thecenter of the fine mark M12 and the center of the second image pickupdevice 3572, i.e., the optical axis of the second lens system 3562 a and3562 b can be precisely determined. The position measuring precisionthrough the fine mark M12 is about 1 μm or less in the example.

The projecting optical system 3560 serving to determine the position ofthe fine mark M12 has a predetermined positional relationship with thelaser annealing irradiation optical system 3520, and the positionalrelationship is determined or adjusted in advance. Accordingly, thedistance from the optical axis of the second lens system 3562 a and 3562b to the center of the fine mark M12 can be converted into the distancefrom the laser annealing irradiation optical system 3520 to the centerof the fine mark M12 with reference to the positional relationship (StepS5). By these procedures, the coordinates of the first alignment mark M1can be precisely determined.

Likewise, the second alignment mark M2 is subjected to these measuringprocedures (steps S1 to S5), and the coordinates of the second alignmentmark M2 can be precisely determined (Step S6). In the example, one pixelof the second image pickup device 3572 was set at 1 μm and the positionwas detected with a precision of about 1 μm.

Next, the work W is aligned (Step 7) with respect to the irradiationoptical system 3520 based on the precise measurements of the coordinatesof the first and second alignment marks M1 and M2 obtained in steps S5and S6. Specifically, the position and rotation of the work W aredetermined based on the coordinate measurements of the fine marks of thefirst and second alignment marks M1 and M2 with reference to theirradiation optical system 3520. Based on these results, the work W isarranged at a position with a rotational attitude required upon theinitiation of laser annealing.

Next, while scanning the work W with the laser light AL such as a laserspot or a laser line using the stage driving unit 3540 and the travelingdistance measuring device 3550, the amorphous thin film on the work W isrecrystallized to sequentially form polycrystalline thin films on thework W. In this procedure, the work W can be scanned with the laserlight AL by moving the stage 3530 in the X or Y direction by the stagedriving unit 3540, while monitoring the travel of the stage with thetraveling distance measuring device 3550. Alternatively, the work W canbe scanned with the laser light AL by allowing the irradiation opticalsystem 3520 to have a scanning function, for example, by moving the mask3520 b in the irradiation optical system 3520.

In the position measuring process according to the first embodiment,after the work W is transferred to and mounted on the stage 3530, theposition of the work W can be precisely determined only by moving thework W through search alignment using the global mark M11, and thus theposition of the work W can be rapidly determined. In addition, theglobal mark M11 and the fine mark M12 have similar-shaped outlines toeach other, and the image measurement algorithms in the measurements ofthe marks M11 and M12 can be nearly the same as each other, and thearithmetic processing and other procedures can be simplified.

FIG. 51 is a perspective view showing arrangement of the alignment marksformed on the surface of the work W mounted on the stage 3530 shown inFIG. 49.

First and second global marks M111 and M211 are respectively formed ineither one of the four corners of the work W. Both global marks M111 andM211 have identical coordinates in the work X axis and differentcoordinates in the work Y axis. Separately, first and second fine marksM 12 and M212 are respectively arranged in the vicinity of processingareas PA on the work W. Both fine marks M112 and M212 have identicalcoordinates in the work X axis and different coordinates in the work Yaxis. The processing areas PA are areas to be projected with, forexample, a slit image of the mask 3520 b by projection lens 3520 c, andare arrayed at appropriate intervals (in the figure, only two processingareas are shown).

The positional measurements of the first and second global marks M111and M211 can determine the coordinates of two reference points on theperiphery of the work W. By this procedure, the attitude of the work Wcan be corrected and the search alignment (global alignment) can beperformed to allow each of the first and second fine marks M112 and M212enter into the image field of the second image pickup device 3572 of ahigh magnification (FIG. 49). Separately, the positional measurements ofthe first and second fine marks M112 and M212 can determine precisecoordinates of two reference points on the periphery of the processingareas PA corresponding to these fine marks. The slit image of the mask3520 b can be therefore precisely projected onto the processing areas PAby appropriately moving the work W.

FIG. 52 is a schematic illustration of the configuration of a laserannealer as an embodiment of the invented laser processing system.

This laser annealer serves to treat a work W with heat, and the work Wcomprises a glass substrate and an amorphous Si or another semiconductorthin film formed on the glass substrate. The laser annealer includes alaser source 5310, an irradiation optical system 5320, a process stageunit 5330, a stage controller 5340, and a master controller 53100. Thelaser source 5310 produces a laser light AL such as an excimer laser forheating the semiconductor thin film. The irradiation optical system 5320converts the laser light AL into a line (to be precise, a finerectangle) and launches the laser light AL onto the work W at apredetermined illumination. The process stage unit 5330 supports thework W and allows the work W to smoothly move in the X-Y plane in atranslational manner and to rotate around the Z axis. The stagecontroller 5340 controls the operations of the process stage unit 5330,and the master controller 53100 generally controls the operations ofindividual components of the laser annealer.

The irradiation optical system 5320 comprises a homogenizer 5320 a, amask 5320 b, and a projection lens 5320 c. The homogenizer 5320 aensures the incident laser light AL to have a uniform distribution. Themask 5320 b has a slit, and the slit throttles the laser light AL passedthrough the homogenizer 3520 a into a rectangular beam. The projectionlens 5320 c reduces and projects the slit image of the mask 5320 b ontothe work W. Of these components, the mask 5320 b is exchangeablysupported by a mask stage unit 5350. The mask stage unit 5350 drives andallows the mask 5320 b to smoothly move in the X-Y plane in atranslational manner and to rotate around the Z axis. The operations ofthe mask stage unit 5350 are controlled by a stage controller 5360 tomonitor the timing and travel of the translation and rotation of themask 5320 b. The mask stage unit 5350 and the stage controller 5360constitute a mask driving unit.

The process stage unit 5330 is housed in a process chamber 5370. Thelaser light AL is launched from the irradiation optical system 5320 viaa process window 5370 a onto the work W supported by the process stageunit 5330 in the process chamber 5370. The translational and rotationaltravels are monitored by the stage controller 5340.

The process window 5370 a is arranged on the top surface of the processchamber 5370. Immediately above the corner of the process window 5370 a,a work alignment camera 5380 is fixed. The work alignment camera 5380serves to detect the misalignment of the work W mounted on the processstage unit 5330, and includes an image-forming optical system and a CCDand other image pickup devices. A picture signal output from the workalignment camera 5380 is subjected to processing in an image processor5381. Signals produced by the image processor 5381 are entered into themaster controller 53100 and are used in the alignment of the work Wrelative to the projection lens 5320 c constituting the irradiationoptical system 5320.

Immediately below a corner of the mask 5320 b, a mask alignment camera5384 as an image pickup device is fixed. The mask alignment camera 5384serves to detect the misalignment of the mask 5320 b supported by themask stage unit 5350, and produces a picture signal output. The picturesignal output from the mask alignment camera 5384 is subjected toprocessing in an image processor 5385, and the picked-up image isdisplayed on a display 5386 as a display device, and is used in thealignment of the mask 5320 b relative to the work W.

In this configuration, the mask stage unit 5350 and the projection lens5320 c are fixed to a frame 5390 extending from the process chamber5370. The mask alignment camera 5384 is also fixed via a supportingmember 5391 to the frame 5390. While the detailed descriptions of thiscomponent are omitted herein, the supporting member 5391 serves toadjust the position of the mask alignment camera 5384 relative to themask stage unit 5350. Specifically, the mask alignment camera 5384 ismoved in the X-Y plane in a translational manner and is rotated aroundthe Z axis, and can be surely fixed to the frame 5390 after thecompletion of necessary alignment movement.

In the above system, the image of a mask alignment mark AM is indicatedon the display 5386 while the mask 5320 b is moved relative to theprojection lens 5320 c by the mask stage unit 5350. By thisconfiguration, the position of the mask 5320 b can be precisely andpositively determined in real time while visually checking the position.

The advantages of the invention will now be listed below.

(1) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected light patterned through pluralpatterns formed on a photo mask, the invented system includes amechanism for uniformizing light for exposure in such a manner that thelight intensity in a predetermined area on the photo mask distributeswithin a range of ±11.2% of the average light intensity in the area. Bythis configuration, a semiconductor thin film on a desired region to bepatterned can be homogeneously modified. When the system is applied toLCDs and other imaging devices, damage of substrates due to variationsin intensity of light source can be prevented to thereby inhibitdeterioration of image quality.

(2) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected light patterned through anexposure pattern formed on a photo mask, and the semiconductor thin filmis formed on a substrate held on a substrate stage, the invented systemincludes a mechanism for sequentially scanning the semiconductor thinfilm with the patterned light by individually or concurrently drivingthe photo mask and the substrate stage. By this configuration, selectedregions on the substrate can be sequentially modified with a highthroughput. When the system is applied to LCDs and other imagingdevices, damage of substrates due to variations in intensity of lightsource can be prevented to thereby inhibit deterioration of imagequality. This system can also provide a crystallized silicon film havinga trap state density less than 10¹² cm⁻².

(3) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected light patterned through anexposure pattern formed on a photo mask, the invented system includes afocusing mechanism for obtaining the focus of the projected patternedlight on the predetermined region of the semiconductor thin film whenthe semiconductor thin film is exposed to the projected patterned light.The above configuration can provide a semiconductor thin film formingsystem having a high reliability in modification processes and asatisfactory reproducibility.

(4) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected exposure beam patterned through apattern formed on a photo mask, the invented system includes a tiltcorrecting mechanism (or a leveling mechanism) for correcting the tiltof the projected patterned beam relative to the semiconductor thin film.The above configuration can provide a semiconductor thin film formingsystem having a high reliability in modification processes and asatisfactory reproducibility.

(5) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected exposure beam patterned through apattern formed on a photo mask, the invented system includes analignment mechanism (or an alignment function) for aligning the exposurebeam relative to a mark formed on a substrate, on which thesemiconductor thin film is deposited. This configuration can achieve theexposure of a target region with an alignment accuracy of the order ofmicrometers or higher. When the system is applied to LCDs and otherimaging devices, damage of substrates due to variations in intensity oflight source can be prevented to thereby inhibit deterioration of imagequality.

(6) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected light patterned through a patternformed on a photo mask, the invented system includes a mechanism (or afunction) for holding a substrate on a stage, the semiconductor thinfilm being deposited on the substrate. The above configuration canprovide a semiconductor thin film forming system having a highreliability in modification processes and a satisfactoryreproducibility.

(7) In a semiconductor thin film forming system for modifying apredetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected exposure beam patterned through apattern formed on a photo mask, the invented system includes a composingmechanism for composing a plurality of laser beams into the exposurebeam. By this configuration, a semiconductor thin film can behomogeneously modified with good quality in target regions to bepatterned. In addition, selected regions on the substrate can besequentially modified with a high throughput.

(8) Preferably in the system just mentioned above in (7), the pluralityof laser beams comprises first and second laser beams, and the composingmechanism composes the first and second laser beams in such a mannerthat the second laser beam is applied onto the semiconductor thin filmwith a delay relative to the first laser beam. By this configuration, asemiconductor thin film can be homogeneously modified with good qualityin target regions to be patterned. In addition, selected regions on thesubstrate can be sequentially modified with a high throughput.

(9) In a semiconductor thin film forming system having a processchamber, the process chamber serves to modify a predetermined region ofa semiconductor thin film by exposing the semiconductor thin film on asubstrate to a projected exposure beam patterned through a patternformed on a photo mask, the invented system includes a mechanism formoving the substrate from the process chamber to a different processchamber without exposing the substrate to the atmosphere (or the air).By this configuration, a semiconductor thin film can be transferred to asuccessive process without contamination by impurities and dusts, whilethe semiconductor thin film has a chemically active surface of anequivalent quality to that of a single crystal semiconductor thin film.Thus, manufacture costs for the semiconductor production system can bereduced by eliminating a cleaning process, and the throughput can beincreased by reducing evacuation periods or cleaning periods inindividual vacuum systems.

(10) In the system just mentioned above (9), preferably the differentprocess chamber is an insulating film forming chamber for the formationof an insulating film on the substrate. By this configuration, asemiconductor thin film can be transferred to a gate insulating filmforming process without contamination by impurities and dusts, while thesemiconductor thin film has a chemically active surface of an equivalentquality to that of a single crystal semiconductor thin film. Thus, asemiconductor element having a satisfactory semiconductor-insulatorinterface can be manufactured by a process at low temperatures of 600°C. or less. Such a good semiconductor-insulator interface isconventionally formed, for example, in an interface between silicon andsilicon oxide formed by heating. This system can provide a crystallizedsilicon film having a trap state density less than 10¹² cm⁻² and canprovide a silicon-insulating film interface exhibiting a low interfacestate density.

(11) In the system indicated in (9), the different process chamber ispreferably a semiconductor film forming chamber for the formation of asemiconductor thin film on the substrate. By this configuration, asemiconductor film can be transferred to a light irradiation processwithout contamination by impurities and dusts, which semiconductor filmis necessary for producing a semiconductor thin film having a chemicallyactive surface of an equivalent quality to that of a single crystalsemiconductor thin film. Thus, manufacture costs for the semiconductordeposition system can be reduced by eliminating a cleaning process, andthe throughput can be increased by reducing evacuation times or cleaningtimes in individual vacuum systems.

(12) In the system indicated in (9), the invention provides a systemwhere the different process chamber is a heat treatment chamber fortreating the substrate with heat.

(13) Preferably, the different process chamber in the system indicatedin (9) is a plasma treatment chamber for subjecting the substrate to aplasma treatment by treating the substrate with plasma. By thisconfiguration, a semiconductor thin film can be transferred to asuccessive process without contamination by impurities and dusts, whilethe semiconductor thin film has a chemically active surface of anequivalent quality to that of a single crystal semiconductor thin film.Thus, manufacture costs for the semiconductor deposition system can bereduced by eliminating a cleaning process, and the throughput can beincreased by reducing evacuation times or cleaning times in individualvacuum systems.

(14) In the system indicated in (9), the process chamber is preferably alaser treatment chamber for modifying the predetermined region of thesemiconductor thin film by exposing the semiconductor thin film on thesubstrate to a projected laser beam patterned through the pattern formedon the photo mask, the different process chamber being preferablyanother laser treatment chamber. By this configuration, a semiconductorthin film can be transferred to a successive process withoutcontamination by impurities and dusts, while the semiconductor thin filmhas a chemically active surface of an equivalent quality to that of asingle crystal semiconductor thin film. Thus, manufacture costs for thesemiconductor production system can be reduced by eliminating a cleaningprocess, and the throughput can be increased by reducing evacuationtimes or cleaning times in individual vacuum systems.

(15) In a preferred embodiment, the different process chamber in thesystem indicated in any one of (9) to (13) includes a plasma generatingsource for generating plasma in a predetermined area of the differentprocess chamber, and the substrate is placed in an area in the differentprocess chamber other than the predetermined area. This configurationcan inhibit plasma-induced damage of the semiconductor thin film, whichsemiconductor thin film is transferred to a successive process withoutcontamination by impurities and dusts and has a chemically activesurface of an equivalent good quality to that of a single crystalsemiconductor thin film.

(16) In the system indicated in (13), preferably, the different processchamber includes a plasma source for generating plasma in apredetermined area of the different process chamber, and the differentprocess chamber serves to subject the substrate to the plasma treatmentby reacting an excited gas with a different gas, the excited gas isexcited by the plasma generated in the predetermined area, and thedifferent gas is introduced into the different process chamber withoutpassing through the predetermined area. Thus, a semiconductor elementhaving a satisfactory semiconductor-insulator interface can bemanufactured by a process at low temperatures of 400° C. or less. Such agood semiconductor-insulator interface is conventionally formed, forexample, in an interface between silicon and silicon oxide formed byheating.

Other embodiments and variations will be obvious to those skilled in theart, and this invention is not to be limited to the specific mattersstated above.

1. (canceled)
 2. A semiconductor thin film forming system for modifyinga predetermined region of a semiconductor thin film by exposing thesemiconductor thin film to a projected light patterned through anexposure pattern formed on a photo mask, said semiconductor thin filmbeing formed on a substrate held on a substrate stage, said systemcomprising a mechanism for sequentially scanning the semiconductor thinfilm with the patterned light by individually or concurrently drivingthe photo mask and the substrate stage. 3-16. (canceled)
 17. The systemaccording to claim 2, wherein said projected light comprises a laserbeam.
 18. The system according to claim 17, wherein said laser beam isgenerated by an eximer laser.
 19. The system according to claim 17,wherein said light is uniformized using a homogenizer, a mask and aprojection lens through which said light is applied.
 20. The sysetmaccording to claim 19, wherein said mask includes a slit for throttlinglight passed through the homogenizer into a rectangular beam.
 21. Asystem according to claim 19, wherein a projection lens is used forreducing and projecting a slit image of the mask onto said film.
 22. Asystem according to claim 2, wherein said predetermined region of thesemiconductor thin film is modified by exposing, at a travel pitch ofthe order of micrometers, the semiconductor thin film to said projectedlight.
 23. A system according to claim 2, wherein said predeterminedregion of the semiconductor thin film is modified by exposing a targetexposure position of the semiconductor thin film to said projected lightwith a target accuracy of 0.1 μm to 100 μm.